runtime: line-buffer goroutine dump output?

[bradfitz]

In #31986, the user's bug report reports a stack dump that's oddly formatted:

panic: 
api_1  | 15:58:21 app         | interface conversion: http.http2Frame is *http.http2UnknownFrame, not *http.http2HeadersFrame
api_1  | 15:58:21 app         | 
api_1  | 15:58:21 app         | 	
api_1  | 15:58:21 app         | panic: 
api_1  | 15:58:21 app         | err must be non-nil
api_1  | 15:58:21 app         | 
api_1  | 15:58:21 app         | 
api_1  | 15:58:21 app         | goroutine 
api_1  | 15:58:21 app         | 32
api_1  | 15:58:21 app         |  [
api_1  | 15:58:21 app         | running
api_1  | 15:58:21 app         | ]:
api_1  | 15:58:21 app         | panic
api_1  | 15:58:21 app         | (
api_1  | 15:58:21 app         | 0x9e0580
api_1  | 15:58:21 app         | , 
api_1  | 15:58:21 app         | 0xbb6070
api_1  | 15:58:21 app         | )
api_1  | 15:58:21 app         | 	
api_1  | 15:58:21 app         | /usr/local/go/src/runtime/panic.go
api_1  | 15:58:21 app         | :
api_1  | 15:58:21 app         | 565
api_1  | 15:58:21 app         |  +
api_1  | 15:58:21 app         | 0x2c5
api_1  | 15:58:21 app         |  fp=
api_1  | 15:58:21 app         | 0xc000407b68
api_1  | 15:58:21 app         |  sp=
api_1  | 15:58:21 app         | 0xc000407ad8
api_1  | 15:58:21 app         |  pc=
api_1  | 15:58:21 app         | 0x42bca5
api_1  | 15:58:21 app         | 
api_1  | 15:58:21 app         | net/http.(*http2pipe).closeWithError
api_1  | 15:58:21 app         | (
api_1  | 15:58:21 app         | 0xc0002d76a8
api_1  | 15:58:21 app         | , 
api_1  | 15:58:21 app         | 0xc0002d76f8
api_1  | 15:58:21 app         | , 
api_1  | 15:58:21 app         | 0x0, 0x0, 0x0)
api_1  | 	/usr/local/go/src/net/http/h2_bundle.go:3553 +0x1cd fp=0xc000407b90 sp=0xc000407b68 pc=0x67d70d
api_1  | 15:58:21 app         | net/http.(*http2pipe).CloseWithError
api_1  | 15:58:21 app         | (...)
api_1  | 	/usr/local/go/src/net/http/h2_bundle.go:3540
api_1  | net/http.(*http2clientConnReadLoop).cleanup(0xc000407fb8)
api_1  | 	/usr/local/go/src/net/http/h2_bundle.go:8084 +0x26c fp=0xc000407c90 sp=0xc000407b90 pc=0x694cac
api_1  | 15:58:21 app         | runtime.call32(0x0, 0xae22d8, 0xc00005a0b0, 0x800000008)
api_1  | 	/usr/local/go/src/runtime/asm_amd64.s:519 +0x3b fp=0xc000407cc0 sp=0xc000407c90 pc=0x45605b
api_1  | panic(0xa18c40, 0xc0005de240)
api_1  | 	/usr/local/go/src/runtime/panic.go:522 +0x1b5 fp=0xc000407d50 sp=0xc000407cc0 pc=0x42bb95
api_1  | 15:58:21 app         | runtime.panicdottypeE
api_1  | 15:58:21 app         | (...)
...

I'm not sure which process supervisor that is, but perhaps Go should internally line-buffer those dumps and only write to stderr on complete lines.

/cc @aclements @cherrymui @ianlancetaylor @rsc

[andybons]

@zhangriyueming can you provide more information on your environment (where this snippet came from)? What are you using to run your programs/what is capturing this output?

Thanks