How to find out which Go version built your binary

gistfile1.txt

% dlv exec $HOME/bin/godoc
Type 'help' for list of commands.
(dlv) b main.main
Breakpoint 1 set at 0x15596eb for main.main() ./golang.org/x/tools/cmd/godoc/main.go:156
(dlv) c
> main.main() ./golang.org/x/tools/cmd/godoc/main.go:156 (hits goroutine(1):1 total:1) (PC: 0x15596eb)
   151:                 }
   152:         }
   153:         log.Fatalf("too many redirects")
   154: }
   155:
=> 156: func main() {
   157:         flag.Usage = usage
   158:         flag.Parse()
   159:
   160:         playEnabled = *showPlayground
   161:
(dlv) p runtime.buildVersion
"go1.8.1"

go version $HOME/bin/godoc