go modules cleanup and remove wrong self import to v1 (#1658)

* Runtime local git, simply go-git code
* go modules cleanup and remove wrong self import to v1
* pin mergo v0.3.8 to avoid panics

Signed-off-by: Máximo Cuadros <mcuadros@gmail.com>
Co-authored-by: Vasiliy Tolstov <v.tolstov@unistack.org>

runtime/local/source/git/git.go

@@ -6,8 +6,8 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/go-git/go-git/v5"
 	"github.com/micro/go-micro/v2/runtime/local/source"
-	git "gopkg.in/src-d/go-git.v4"
 )
 
 // Source retrieves source code