Add test and fix Exec() call

Author: arp242

autoload/go/tool_test.vim

@@ -0,0 +1,23 @@
+func! Test_ExecuteInDir() abort
+  let l:tmp = gotest#write_file('a/a.go', ['package a'])
+  try
+    let l:out = go#tool#ExecuteInDir("pwd")
+    call assert_equal(l:tmp . "/src/a\n", l:out)
+  finally
+    call delete(l:tmp, 'rf')
+  endtry
+endfunc
+
+func! Test_ExecuteInDir_nodir() abort
+  let l:tmp = go#util#tempdir("executeindir")
+  exe ':e ' . l:tmp . '/new-dir/a'
+
+  try
+    let l:out = go#tool#ExecuteInDir("pwd")
+    call assert_equal('', l:out)
+  finally
+    call delete(l:tmp, 'rf')
+  endtry
+endfunc
+
+" vim: sw=2 ts=2 et