I tried the following code on Galaxy S4 with Android 4.4.2:

package main
import (
"golang.org/x/mobile/app"
"golang.org/x/mobile/event/lifecycle"
"golang.org/x/mobile/event/paint"
"os"
)
func main() {
os.Create("zzz.txt")
app.Main(func(a app.App) {
for e := range a.Events() {
switch e := a.Filter(e).(type) {
case lifecycle.Event:
_=e
case paint.Event:
a.Publish()
}
}
})
}

However no file is created in the phone. I tried to specify a path but doesn't help.

I also tried an app called "AnGoIde" which allow us to write Go and compile directly in Android, and the following code is able to create the "zzz.txt" file:

package main
import "os"
func main(){
os.Create("zzz.txt")
}