Hoverfly crash when processing simultaneous requests

[john4744]

I'm running in simulation mode (though I've hit a similar crash in capture mode too). The simulation is stateful. Here's the error message: fatal error: concurrent map read and map write.
It seems like access to the State map isn't synchronized.

Here is the full dump

fatal error: concurrent map read and map write

goroutine 72 [running]:
runtime.throw(0xac457f, 0x21)
 C:/Go/src/runtime/panic.go:616 +0x88 fp=0xc042faaad8 sp=0xc042faaab8 pc=0x42c6b8
runtime.mapaccess1_faststr(0x9f9ae0, 0xc04274ff80, 0xc0426955b0, 0xb, 0xc042982698)
 C:/Go/src/runtime/hashmap_fast.go:181 +0x428 fp=0xc042faab48 sp=0xc042faaad8 pc=0x40a358
github.com/SpectoLabs/hoverfly/core/matching.StateMatcher(0xc042004e50, 0xc042260450, 0xab123a)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/state_matcher.go:21 +0x160 fp=0xc042faac18 sp=0xc042faab48 pc=0x84ab50
github.com/SpectoLabs/hoverfly/core/matching.MatchingStrategyRunner(0xc04347c174, 0x3d, 0xc04347c150, 0x3, 0xc04347c15b, 0x19, 0xc04347c154, 0x4, 0xc042c3a6f0, 0x0, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/matching_strategy_runner.go:36 +0x481 fp=0xc042fab100 sp=0xc042faac18 pc=0x84a431
github.com/SpectoLabs/hoverfly/core/matching.Match(0xab2f32, 0x9, 0xc04347c174, 0x3d, 0xc04347c150, 0x3, 0xc04347c15b, 0x19, 0xc04347c154, 0x4, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/matcher.go:12 +0x192 fp=0xc042fab1b0 sp=0xc042fab100 pc=0x849f82
github.com/SpectoLabs/hoverfly/core.(*Hoverfly).GetResponse(0xc0421f3900, 0xc04347c174, 0x3d, 0xc04347c150, 0x3, 0xc04347c15b, 0x19, 0xc04347c154, 0x4, 0xc042c3a6f0, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/hoverfly_funcs.go:63 +0x3bc fp=0xc042fab408 sp=0xc042fab1b0 pc=0x94ecec
github.com/SpectoLabs/hoverfly/core/modes.SimulateMode.Process(0xbc25e0, 0xc0421f3900, 0xab2f32, 0x9, 0xc042480800, 0xc04347c174, 0x3d, 0xc04347c150, 0x3, 0xc04347c15b, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/modes/simulate_mode.go:44 +0xc4 fp=0xc042fab7d0 sp=0xc042fab408 pc=0x85e464
github.com/SpectoLabs/hoverfly/core/modes.(*SimulateMode).Process(0xc0420afd40, 0xc042480800, 0xc04347c174, 0x3d, 0xc04347c150, 0x3, 0xc04347c15b, 0x19, 0xc04347c154, 0x4, ...)
 <autogenerated>:1 +0xa8 fp=0xc042fab890 sp=0xc042fab7d0 pc=0x85ff88
github.com/SpectoLabs/hoverfly/core.(*Hoverfly).processRequest(0xc0421f3900, 0xc042480800, 0xf9dfe0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/hoverfly.go:187 +0x16a fp=0xc042faba38 sp=0xc042fab890 pc=0x94e42a
github.com/SpectoLabs/hoverfly/core.NewProxy.func4(0xc042480800, 0xc0427fe500, 0xc0427fe500, 0x1)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/proxy.go:67 +0x71 fp=0xc042fabac0 sp=0xc042faba38 pc=0x9589c1
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.FuncReqHandler.Handle(0xc042fb3d40, 0xc042480800, 0xc0427fe500, 0x1, 0x10)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/actions.go:19 +0x41 fp=0xc042fabaf0 sp=0xc042fabac0 pc=0x6eaea1
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ReqProxyConds).Do.func1(0xc042480800, 0xc0427fe500, 0x1406a8, 0x0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/dispatcher.go:200 +0xe8 fp=0xc042fabb50 sp=0xc042fabaf0 pc=0x6f0f88
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.FuncReqHandler.Handle(0xc0427e4b60, 0xc042480800, 0xc0427fe500, 0x40dd11, 0x10)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/actions.go:19 +0x41 fp=0xc042fabb80 sp=0xc042fabb50 pc=0x6eaea1
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ProxyHttpServer).filterRequest(0xc0421e4000, 0xc042480800, 0xc0427fe500, 0xc042a53d08, 0x4)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/proxy.go:55 +0x99 fp=0xc042fabbd0 sp=0xc042fabb80 pc=0x6eeef9
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ProxyHttpServer).ServeHTTP(0xc0421e4000, 0xbc6520, 0xc04293a0e0, 0xc042480800)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/proxy.go:112 +0x2ae fp=0xc042fabd58 sp=0xc042fabbd0 pc=0x6ef4be
net/http.serverHandler.ServeHTTP(0xc042090750, 0xbc6520, 0xc04293a0e0, 0xc042480800)
 C:/Go/src/net/http/server.go:2694 +0xc3 fp=0xc042fabd88 sp=0xc042fabd58 pc=0x6a3c33
net/http.(*conn).serve(0xc0435fa320, 0xbc6b20, 0xc043393880)
 C:/Go/src/net/http/server.go:1830 +0x658 fp=0xc042fabfc8 sp=0xc042fabd88 pc=0x69ff58
runtime.goexit()
 C:/Go/src/runtime/asm_amd64.s:2361 +0x1 fp=0xc042fabfd0 sp=0xc042fabfc8 pc=0x456731
created by net/http.(*Server).Serve
 C:/Go/src/net/http/server.go:2795 +0x282

goroutine 1 [IO wait]:
internal/poll.runtime_pollWait(0x1cb740, 0x72, 0xbc1640)
 C:/Go/src/runtime/netpoll.go:173 +0x5e
internal/poll.(*pollDesc).wait(0xc04275ef88, 0x72, 0xe9d500, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_poll_runtime.go:85 +0xa2
internal/poll.(*ioSrv).ExecIO(0xf9adf8, 0xc04275edd8, 0xc04242c2a0, 0x1, 0x0, 0x1a0)
 C:/Go/src/internal/poll/fd_windows.go:223 +0x13a
internal/poll.(*FD).acceptOne(0xc04275edc0, 0x1a0, 0xc042312620, 0x2, 0x2, 0xc04275edd8, 0x4ceba9, 0xc04207a290, 0x41080f, 0x10)
 C:/Go/src/internal/poll/fd_windows.go:793 +0xae
internal/poll.(*FD).Accept(0xc04275edc0, 0xc04207ccd0, 0x0, 0x0, 0x0, 0x0, 0xc000000000, 0x0, 0x0, 0x0, ...)
 C:/Go/src/internal/poll/fd_windows.go:827 +0x142
net.(*netFD).accept(0xc04275edc0, 0xc042a36080, 0xc04207a400, 0x4022f8)
 C:/Go/src/net/fd_windows.go:192 +0x86
net.(*TCPListener).accept(0xc042004ed0, 0xc04207a430, 0x40119e, 0xc042a36080)
 C:/Go/src/net/tcpsock_posix.go:136 +0x35
net.(*TCPListener).AcceptTCP(0xc042004ed0, 0xc04207a478, 0xc04207a480, 0x18)
 C:/Go/src/net/tcpsock.go:246 +0x50
net/http.tcpKeepAliveListener.Accept(0xc042004ed0, 0xb21788, 0xc042a36000, 0xbc6be0, 0xc042dd5020)
 C:/Go/src/net/http/server.go:3216 +0x36
net/http.(*Server).Serve(0xc0420909c0, 0xbc6920, 0xc042004ed0, 0x0, 0x0)
 C:/Go/src/net/http/server.go:2770 +0x1ac
net/http.(*Server).ListenAndServe(0xc0420909c0, 0xc0420909c0, 0xc042c36000)
 C:/Go/src/net/http/server.go:2711 +0xb0
net/http.ListenAndServe(0xc042723f80, 0xe, 0xbbfa40, 0xc042dd4ea0, 0x2, 0xc042723f80)
 C:/Go/src/net/http/server.go:2969 +0x81
github.com/SpectoLabs/hoverfly/core.(*AdminApi).StartAdminInterface(0xc04207a838, 0xc0421f3900)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/admin.go:38 +0x4f2
main.main()
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/cmd/hoverfly/main.go:438 +0x150b

goroutine 38 [IO wait]:
internal/poll.runtime_pollWait(0x1cb810, 0x72, 0xbc1640)
 C:/Go/src/runtime/netpoll.go:173 +0x5e
internal/poll.(*pollDesc).wait(0xc04275ecc8, 0x72, 0xe9d500, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_poll_runtime.go:85 +0xa2
internal/poll.(*ioSrv).ExecIO(0xf9adf8, 0xc04275eb18, 0xc042af7c40, 0x1, 0x0, 0xf4)
 C:/Go/src/internal/poll/fd_windows.go:223 +0x13a
internal/poll.(*FD).acceptOne(0xc04275eb00, 0xf4, 0xc0423127e0, 0x2, 0x2, 0xc04275eb18, 0xc0424a3ca8, 0xc0424a3c88, 0x41080f, 0x10)
 C:/Go/src/internal/poll/fd_windows.go:793 +0xae
internal/poll.(*FD).Accept(0xc04275eb00, 0xc043356b40, 0x0, 0x0, 0x0, 0x0, 0xc000000000, 0x0, 0x0, 0x0, ...)
 C:/Go/src/internal/poll/fd_windows.go:827 +0x142
net.(*netFD).accept(0xc04275eb00, 0x0, 0xc0424a3e20, 0x58afb3)
 C:/Go/src/net/fd_windows.go:192 +0x86
net.(*TCPListener).accept(0xc042004e88, 0xf9dfe0, 0x0, 0x0)
 C:/Go/src/net/tcpsock_posix.go:136 +0x35
net.(*TCPListener).Accept(0xc042004e88, 0xbed830e7adecdd08, 0x4b77b15b9, 0xf9dfe0, 0x0)
 C:/Go/src/net/tcpsock.go:259 +0x50
github.com/SpectoLabs/hoverfly/core.(*StoppableListener).Accept(0xc042fb3ef0, 0xb21788, 0xc042a361e0, 0xbc6be0, 0xc042c3a0c0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/listener.go:37 +0x84
net/http.(*Server).Serve(0xc042090750, 0xbc5520, 0xc042fb3ef0, 0x0, 0x0)
 C:/Go/src/net/http/server.go:2770 +0x1ac
github.com/SpectoLabs/hoverfly/core.(*Hoverfly).StartProxy.func1(0xc0421f3900, 0xc042090750, 0xc042fb3ef0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/hoverfly.go:165 +0xdc
created by github.com/SpectoLabs/hoverfly/core.(*Hoverfly).StartProxy
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/hoverfly.go:158 +0x4ee

goroutine 28 [runnable]:
github.com/SpectoLabs/hoverfly/core/matching.(*StrongestMatchStrategy).Matching(0xc04225e690, 0xc04335bf90, 0xaaef67, 0x5)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/strongest_match_strategy.go:30 +0x1a1
github.com/SpectoLabs/hoverfly/core/matching.MatchingStrategyRunner(0xc0428e81e4, 0x3d, 0xc0428e81c0, 0x3, 0xc0428e81cb, 0x19, 0xc0428e81c4, 0x4, 0xc0426deba0, 0x0, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/matching_strategy_runner.go:36 +0x4ba
github.com/SpectoLabs/hoverfly/core/matching.Match(0xab2f32, 0x9, 0xc0428e81e4, 0x3d, 0xc0428e81c0, 0x3, 0xc0428e81cb, 0x19, 0xc0428e81c4, 0x4, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/matcher.go:12 +0x192
github.com/SpectoLabs/hoverfly/core.(*Hoverfly).GetResponse(0xc0421f3900, 0xc0428e81e4, 0x3d, 0xc0428e81c0, 0x3, 0xc0428e81cb, 0x19, 0xc0428e81c4, 0x4, 0xc0426deba0, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/hoverfly_funcs.go:63 +0x3bc
github.com/SpectoLabs/hoverfly/core/modes.SimulateMode.Process(0xbc25e0, 0xc0421f3900, 0xab2f32, 0x9, 0xc042480900, 0xc0428e81e4, 0x3d, 0xc0428e81c0, 0x3, 0xc0428e81cb, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/modes/simulate_mode.go:44 +0xc4
github.com/SpectoLabs/hoverfly/core.(*Hoverfly).processRequest(0xc0421f3900, 0xc042480900, 0xf9dfe0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/hoverfly.go:187 +0x16a
github.com/SpectoLabs/hoverfly/core.NewProxy.func4(0xc042480900, 0xc04225e5f0, 0xc04225e5f0, 0x1)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/proxy.go:67 +0x71
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.FuncReqHandler.Handle(0xc042fb3d40, 0xc042480900, 0xc04225e5f0, 0x1, 0x10)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/actions.go:19 +0x41
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ReqProxyConds).Do.func1(0xc042480900, 0xc04225e5f0, 0x140d50, 0x0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/dispatcher.go:200 +0xe8
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.FuncReqHandler.Handle(0xc0427e4b60, 0xc042480900, 0xc04225e5f0, 0x40dd11, 0x10)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/actions.go:19 +0x41
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ProxyHttpServer).filterRequest(0xc0421e4000, 0xc042480900, 0xc04225e5f0, 0xc042a57d08, 0x4)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/proxy.go:55 +0x99
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ProxyHttpServer).ServeHTTP(0xc0421e4000, 0xbc6520, 0xc0421361c0, 0xc042480900)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/proxy.go:112 +0x2ae
net/http.serverHandler.ServeHTTP(0xc042090750, 0xbc6520, 0xc0421361c0, 0xc042480900)
 C:/Go/src/net/http/server.go:2694 +0xc3
net/http.(*conn).serve(0xc042a36140, 0xbc6b20, 0xc043393900)
 C:/Go/src/net/http/server.go:1830 +0x658
created by net/http.(*Server).Serve
 C:/Go/src/net/http/server.go:2795 +0x282

goroutine 29 [runnable]:
github.com/SpectoLabs/hoverfly/core/matching.(*StrongestMatchStrategy).PreMatching(0xc0420bd130)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/strongest_match_strategy.go:24 +0x45
github.com/SpectoLabs/hoverfly/core/matching.MatchingStrategyRunner(0xc042018414, 0x3d, 0xc0420183f0, 0x3, 0xc0420183fb, 0x19, 0xc0420183f4, 0x4, 0xc043488de0, 0x0, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/matching_strategy_runner.go:18 +0x14b
github.com/SpectoLabs/hoverfly/core/matching.Match(0xab2f32, 0x9, 0xc042018414, 0x3d, 0xc0420183f0, 0x3, 0xc0420183fb, 0x19, 0xc0420183f4, 0x4, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/matching/matcher.go:12 +0x192
github.com/SpectoLabs/hoverfly/core.(*Hoverfly).GetResponse(0xc0421f3900, 0xc042018414, 0x3d, 0xc0420183f0, 0x3, 0xc0420183fb, 0x19, 0xc0420183f4, 0x4, 0xc043488de0, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/hoverfly_funcs.go:63 +0x3bc
github.com/SpectoLabs/hoverfly/core/modes.SimulateMode.Process(0xbc25e0, 0xc0421f3900, 0xab2f32, 0x9, 0xc042480a00, 0xc042018414, 0x3d, 0xc0420183f0, 0x3, 0xc0420183fb, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/modes/simulate_mode.go:44 +0xc4
github.com/SpectoLabs/hoverfly/core.(*Hoverfly).processRequest(0xc0421f3900, 0xc042480a00, 0xf9dfe0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/hoverfly.go:187 +0x16a
github.com/SpectoLabs/hoverfly/core.NewProxy.func4(0xc042480a00, 0xc0420bd090, 0xc0420bd090, 0x1)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/proxy.go:67 +0x71
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.FuncReqHandler.Handle(0xc042fb3d40, 0xc042480a00, 0xc0420bd090, 0x1, 0x10)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/actions.go:19 +0x41
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ReqProxyConds).Do.func1(0xc042480a00, 0xc0420bd090, 0x140000, 0x0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/dispatcher.go:200 +0xe8
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.FuncReqHandler.Handle(0xc0427e4b60, 0xc042480a00, 0xc0420bd090, 0x40dd11, 0x10)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/actions.go:19 +0x41
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ProxyHttpServer).filterRequest(0xc0421e4000, 0xc042480a00, 0xc0420bd090, 0xc042f77d08, 0x4)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/proxy.go:55 +0x99
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ProxyHttpServer).ServeHTTP(0xc0421e4000, 0xbc6520, 0xc04287e1c0, 0xc042480a00)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/proxy.go:112 +0x2ae
net/http.serverHandler.ServeHTTP(0xc042090750, 0xbc6520, 0xc04287e1c0, 0xc042480a00)
 C:/Go/src/net/http/server.go:2694 +0xc3
net/http.(*conn).serve(0xc042a361e0, 0xbc6b20, 0xc043393a00)
 C:/Go/src/net/http/server.go:1830 +0x658
created by net/http.(*Server).Serve
 C:/Go/src/net/http/server.go:2795 +0x282

goroutine 71 [runnable]:
bytes.makeSlice(0x200, 0x1536f0, 0x0, 0xc0421aa030)
 C:/Go/src/bytes/buffer.go:223 +0xb7
bytes.(*Buffer).grow(0xc042d26230, 0x200, 0xc0435074a0)
 C:/Go/src/bytes/buffer.go:144 +0x158
bytes.(*Buffer).Grow(0xc042d26230, 0x200)
 C:/Go/src/bytes/buffer.go:163 +0x41
io/ioutil.readAll(0x1cb940, 0xc04335cbe0, 0x200, 0x0, 0x0, 0x0, 0x0, 0x0)
 C:/Go/src/io/ioutil/ioutil.go:34 +0x9a
io/ioutil.ReadAll(0x1cb940, 0xc04335cbe0, 0xc04335cbe0, 0x1cb940, 0xc04335cbe0, 0x0, 0x0)
 C:/Go/src/io/ioutil/ioutil.go:45 +0x45
github.com/SpectoLabs/hoverfly/core/util.GetRequestBody(0xc042480700, 0xc0420a7dd0, 0x0, 0xc0421aa030, 0x0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/util/util.go:24 +0x67
github.com/SpectoLabs/hoverfly/core/models.NewRequestDetailsFromHttpRequest(0xc042480700, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/models/payload.go:73 +0x79
github.com/SpectoLabs/hoverfly/core/journal.(*Journal).NewEntry(0xc0420afd20, 0xc042480700, 0xc0434122d0, 0xab227d, 0x8, 0xbed830e76decdd08, 0x47be04bb9, 0xf9dfe0, 0x19, 0x1)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/journal/journal.go:44 +0x9e
github.com/SpectoLabs/hoverfly/core.NewProxy.func4(0xc042480700, 0xc0433be500, 0xc0433be500, 0x1)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/core/proxy.go:68 +0xd1
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.FuncReqHandler.Handle(0xc042fb3d40, 0xc042480700, 0xc0433be500, 0x1, 0x10)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/actions.go:19 +0x41
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ReqProxyConds).Do.func1(0xc042480700, 0xc0433be500, 0x1536f0, 0x0)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/dispatcher.go:200 +0xe8
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.FuncReqHandler.Handle(0xc0427e4b60, 0xc042480700, 0xc0433be500, 0x40dd11, 0x10)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/actions.go:19 +0x41
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ProxyHttpServer).filterRequest(0xc0421e4000, 0xc042480700, 0xc0433be500, 0xc042a55d08, 0x4)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/proxy.go:55 +0x99
github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy.(*ProxyHttpServer).ServeHTTP(0xc0421e4000, 0xbc6520, 0xc0434741c0, 0xc042480700)
 C:/Users/john4744/go/src/github.com/SpectoLabs/hoverfly/vendor/github.com/SpectoLabs/goproxy/proxy.go:112 +0x2ae
net/http.serverHandler.ServeHTTP(0xc042090750, 0xbc6520, 0xc0434741c0, 0xc042480700)
 C:/Go/src/net/http/server.go:2694 +0xc3
net/http.(*conn).serve(0xc0435fa280, 0xbc6b20, 0xc043393800)
 C:/Go/src/net/http/server.go:1830 +0x658
created by net/http.(*Server).Serve
 C:/Go/src/net/http/server.go:2795 +0x282

goroutine 73 [IO wait]:
internal/poll.runtime_pollWait(0x1cb5a0, 0x72, 0xbc1640)
 C:/Go/src/runtime/netpoll.go:173 +0x5e
internal/poll.(*pollDesc).wait(0xc0428a7a88, 0x72, 0xe9d500, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_poll_runtime.go:85 +0xa2
internal/poll.(*ioSrv).ExecIO(0xf9adf8, 0xc0428a78d8, 0xb21558, 0x516f3333386e6261, 0x524e30626137576b, 0x5073423255517864)
 C:/Go/src/internal/poll/fd_windows.go:223 +0x13a
internal/poll.(*FD).Read(0xc0428a78c0, 0xc043488a91, 0x1, 0x1, 0x0, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_windows.go:484 +0x248
net.(*netFD).Read(0xc0428a78c0, 0xc043488a91, 0x1, 0x1, 0x70583774526d5654, 0x376c463337675141, 0x32434f4b41655446)
 C:/Go/src/net/fd_windows.go:151 +0x56
net.(*conn).Read(0xc0428aa040, 0xc043488a91, 0x1, 0x1, 0x0, 0x0, 0x0)
 C:/Go/src/net/net.go:176 +0x71
net/http.(*connReader).backgroundRead(0xc043488a80)
 C:/Go/src/net/http/server.go:668 +0x61
created by net/http.(*connReader).startBackgroundRead
 C:/Go/src/net/http/server.go:664 +0xd5

goroutine 43 [runnable]:
net/http.(*connReader).backgroundRead(0xc043488cc0)
 C:/Go/src/net/http/server.go:667
created by net/http.(*connReader).startBackgroundRead
 C:/Go/src/net/http/server.go:664 +0xd5

goroutine 53 [IO wait]:
internal/poll.runtime_pollWait(0x1cb670, 0x72, 0xbc1640)
 C:/Go/src/runtime/netpoll.go:173 +0x5e
internal/poll.(*pollDesc).wait(0xc0428a7d48, 0x72, 0xe9d500, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_poll_runtime.go:85 +0xa2
internal/poll.(*ioSrv).ExecIO(0xf9adf8, 0xc0428a7b98, 0xb21558, 0xc042480500, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_windows.go:223 +0x13a
internal/poll.(*FD).Read(0xc0428a7b80, 0xc043488b51, 0x1, 0x1, 0x0, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_windows.go:484 +0x248
net.(*netFD).Read(0xc0428a7b80, 0xc043488b51, 0x1, 0x1, 0x0, 0x0, 0x0)
 C:/Go/src/net/fd_windows.go:151 +0x56
net.(*conn).Read(0xc0428aa048, 0xc043488b51, 0x1, 0x1, 0x0, 0x0, 0x0)
 C:/Go/src/net/net.go:176 +0x71
net/http.(*connReader).backgroundRead(0xc043488b40)
 C:/Go/src/net/http/server.go:668 +0x61
created by net/http.(*connReader).startBackgroundRead
 C:/Go/src/net/http/server.go:664 +0xd5

goroutine 30 [IO wait]:
internal/poll.runtime_pollWait(0x1cb4d0, 0x72, 0xbc1640)
 C:/Go/src/runtime/netpoll.go:173 +0x5e
internal/poll.(*pollDesc).wait(0xc0434a3248, 0x72, 0xe9d500, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_poll_runtime.go:85 +0xa2
internal/poll.(*ioSrv).ExecIO(0xf9adf8, 0xc0434a3098, 0xb21558, 0x0, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_windows.go:223 +0x13a
internal/poll.(*FD).Read(0xc0434a3080, 0xc043488c11, 0x1, 0x1, 0x0, 0x0, 0x0)
 C:/Go/src/internal/poll/fd_windows.go:484 +0x248
net.(*netFD).Read(0xc0434a3080, 0xc043488c11, 0x1, 0x1, 0x0, 0x0, 0x0)
 C:/Go/src/net/fd_windows.go:151 +0x56
net.(*conn).Read(0xc0423d4958, 0xc043488c11, 0x1, 0x1, 0x0, 0x0, 0x0)
 C:/Go/src/net/net.go:176 +0x71
net/http.(*connReader).backgroundRead(0xc043488c00)
 C:/Go/src/net/http/server.go:668 +0x61
created by net/http.(*connReader).startBackgroundRead
 C:/Go/src/net/http/server.go:664 +0xd5

[john4744]

Not sure if this is a good idea or not... but I just added some basic locking using a RWMutex on State. This seemed to resolve the crashes I was seeing (in simulation and capture). Here's a diff master...john4744:sync-state
If this sounds like the right approach, I'll submit a PR.

[benjih]

Hey @john4744,

What you have said makes complete sense and I think the approach you have taken looks right. My only niggle with it is in core/matching/strongest_match_strategy.go you create a copy of the state while locking and unlocking it, but you do not do the same in core/matching/state_matcher.go. If you could update the state_matcher.go file to use a copy of the state, I think this would be just that little bit better.

Would definitely love a PR though, as it looks great and looks like something we should definitely solve.