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Standard Go environment, and some details.

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/rpjday/.cache/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/rpjday/go"
GORACE=""
GOROOT="/usr/lib/golang"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/golang/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build110643148=/tmp/go-build -gno-record-gcc-switches"
$

$ go help environment
The go command, and the tools it invokes, examine a few different
environment variables. For many of these, you can see the default
value of on your system by running 'go env NAME', where NAME is the
name of the variable.

General-purpose environment variables:

	GCCGO
		The gccgo command to run for 'go build -compiler=gccgo'.
	GOARCH
		The architecture, or processor, for which to compile code.
		Examples are amd64, 386, arm, ppc64.
	GOBIN
		The directory where 'go install' will install a command.
	GOOS
		The operating system for which to compile code.
		Examples are linux, darwin, windows, netbsd.
	GOPATH
		For more details see: 'go help gopath'.
	GORACE
		Options for the race detector.
		See https://golang.org/doc/articles/race_detector.html.
	GOROOT
		The root of the go tree.
	GOTMPDIR
		The directory where the go command will write
		temporary source files, packages, and binaries.
	GOCACHE
		The directory where the go command will store
		cached information for reuse in future builds.

Environment variables for use with cgo:

	CC
		The command to use to compile C code.
	CGO_ENABLED
		Whether the cgo command is supported. Either 0 or 1.
	CGO_CFLAGS
		Flags that cgo will pass to the compiler when compiling
		C code.
	CGO_CFLAGS_ALLOW
		A regular expression specifying additional flags to allow
		to appear in #cgo CFLAGS source code directives.
		Does not apply to the CGO_CFLAGS environment variable.
	CGO_CFLAGS_DISALLOW
		A regular expression specifying flags that must be disallowed
		from appearing in #cgo CFLAGS source code directives.
		Does not apply to the CGO_CFLAGS environment variable.
	CGO_CPPFLAGS, CGO_CPPFLAGS_ALLOW, CGO_CPPFLAGS_DISALLOW
		Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
		but for the C preprocessor.
	CGO_CXXFLAGS, CGO_CXXFLAGS_ALLOW, CGO_CXXFLAGS_DISALLOW
		Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
		but for the C++ compiler.
	CGO_FFLAGS, CGO_FFLAGS_ALLOW, CGO_FFLAGS_DISALLOW
		Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
		but for the Fortran compiler.
	CGO_LDFLAGS, CGO_LDFLAGS_ALLOW, CGO_LDFLAGS_DISALLOW
		Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
		but for the linker.
	CXX
		The command to use to compile C++ code.
	PKG_CONFIG
		Path to pkg-config tool.

Architecture-specific environment variables:

	GOARM
		For GOARCH=arm, the ARM architecture for which to compile.
		Valid values are 5, 6, 7.
	GO386
		For GOARCH=386, the floating point instruction set.
		Valid values are 387, sse2.
	GOMIPS
		For GOARCH=mips{,le}, whether to use floating point instructions.
		Valid values are hardfloat (default), softfloat.

Special-purpose environment variables:

	GOROOT_FINAL
		The root of the installed Go tree, when it is
		installed in a location other than where it is built.
		File names in stack traces are rewritten from GOROOT to
		GOROOT_FINAL.
	GO_EXTLINK_ENABLED
		Whether the linker should use external linking mode
		when using -linkmode=auto with code that uses cgo.
		Set to 0 to disable external linking mode, 1 to enable it.
	GIT_ALLOW_PROTOCOL
		Defined by Git. A colon-separated list of schemes that are allowed to be used
		with git fetch/clone. If set, any scheme not explicitly mentioned will be
		considered insecure by 'go get'.
$