net: JoinHostPort() enclose IPv6 in square brackets even if host is already in this format

[jleroy]

What version of Go are you using (go version)?

go version go1.8.1 darwin/amd64

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/jonathan/go"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/fb/736129595jl9p0x2nsxx2lmh0000gn/T/go-build264978375=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"

What did you do?

https://play.golang.org/p/nrIZqsxHIY

What did you expect to see?

[[fd41:9eff:c33::1b:ffff]]:5672

What did you see instead?

[fd41:9eff:c33::1b:ffff]:5672

[bradfitz]

Your input is invalid. JoinHostPort expects a host name, which does include square brackets. The square brackets are only valid when joined with a port.

[bradfitz]

Note that JoinHostPort doesn't do any sanitization of your host (e.g. https://play.golang.org/p/cbnk8RrQNy).

The existing docs say exactly what it does:

JoinHostPort combines host and port into a network address of the form "host:port" or, if host
contains a colon or a percent sign, "[host]:port".

I'm not sure there's anything to do here.