Go: Add '*.exe~' to .gitignore

When you build a Go executable, which does already exists and is in use on Windows (e.g. running) then the output binary name will be extended by a '~' prefix.
558eeb2d85/src/cmd/go/internal/work/exec.go (L1165-L1170)

Go.gitignore

@@ -1,5 +1,6 @@
 # Binaries for programs and plugins
 *.exe
+*.exe~
 *.dll
 *.so
 *.dylib