Accept test selection regex on :GoDebugTest

[nathanjordan]

Source file

package main

import "testing"

func TestFailure(t *testing.T) {
	t.Fatal("not implemented")
}

func TestHelloWorld(t *testing.T) {
}

:GoDebugTest

Type 'help' for list of commands.
--- FAIL: TestFailure (0.00s)
        main_test.go:6: not implemented
FAIL
/Users/nathan/.cache/nvim/vim-godebug/63271502391631:1: Process 6470 has exited with status 1
(dlv)

:GoDebugTest TestHelloWorld

Type 'help' for list of commands.
PASS
/Users/nathan/.cache/nvim/vim-godebug/63271502391631:1: Process 6565 has exited with status 0
(dlv)