I ran into an issue recently where I was using Go 1.11 features in an application but had Go 1.10 installed on the system. To build I was installing Go 1.11 via go get golang.org/dl/go1.11 && go1.11 download and then starting my build by calling go generate. My code generation also requires Go 1.11, but the go:generate line looks something like this:

//go:generate go run gen.go

However, this uses the version of Go on the system and the build fails because it needs to be using Go 1.11. I can't simply change this to go1.11 run gen.go because on other systems it's being built on (most of them, in fact) Go 1.11 is the default and I'm not downloading it from golang.org/dl.

To work around this, I've moved generation out into a script:

#!/bin/sh

/proc/$PPID/exe run gen.go 

and changed the generate line to invoke this:

//go:generate ./gen.sh

However, this only works if /proc is mounted which feels poor.
It would be nice if the Go binary that ran generate could be passed in for substitution, eg. maybe as $GO. This way the same binary could be invoked:

//go:generate $GO run gen.go