[!GOOS:windows] [!exec:/bin/sh] skip
[!GOOS:windows] chmod 0755 $WORK/bin/go1.999testpath
[!GOOS:plan9] env PATH=$WORK/bin${:}$PATH
[GOOS:plan9] env path=$WORK/bin${:}$path
[GOOS:plan9] replace /bin/sh /bin/rc $WORK/bin/go1.999testpath

# Plain go version
go version
! stdout go1\.999

# GOTOOLCHAIN from PATH
env GOTOOLCHAIN=go1.999testpath
go version
[!GOOS:windows] stdout 'go1.999testpath here!'
[GOOS:windows] stdout 'pretend we ran .*go1.999testpath'

# GOTOOLCHAIN from PATH, with forced subprocess
env GOTOOLCHAIN=go1.999testpath
env GODEBUG=gotoolchainexec=0
go version
[!GOOS:windows] stdout 'go1.999testpath here!'
[GOOS:windows] stdout 'pretend we ran .*go1.999testpath'
env GODEBUG=

# GOTOOLCHAIN from network
env GOTOOLCHAIN=go1.999testmod
go version
stderr 'go: downloading go1.999testmod \(.*/.*\)'
[!GOOS:windows] stdout 'go1.999testmod here!'
[GOOS:windows] stdout 'pretend we ran .*go1.999testmod.*\\bin\\go'

# GOTOOLCHAIN from network, does not exist
env GOTOOLCHAIN=go1.9999x
! go version
stderr 'go: download go1.9999x for .*: toolchain not available'

-- $WORK/bin/go1.999testpath --
#!/bin/sh
echo go1.999testpath here!
-- $WORK/bin/go1.999testpath.bat --
This should say:
	@echo go1.999testpath here!
but exec.Command does not directly support batch files.
execGoToolchain in cmd/go/toolchain.go picks off versions
named go1.999test and instead of running them just runs
cmd /c "echo pretend we ran <file>".

Since the real toolchain will have an exe file and cmd is an
exe file, this seems like a good enough test.
Changing execGoToolchain to use cmd /c to run the batch file
hangs for unknown reasons.