How can I build a Go executable in a Docker container that can be executed on MacOS or Windows

[janbaer]

To build an executable for another platform than the current platform (Docker is running on a Linux OS) you've to set the GOOS environment variable. So you can build executable binaries for MacOS (darwin) and Windows platforms.

GOOS=darwin GOARCH=amd64 go build
GOOS=windows GOARCH=386 go build
GOOS=linux GOARCH=amd64 go build

To find out which platform you've to define for your current system, you can install the node module go-platform. This return the current os and cpu-architecture.