ci: add Lint check on commits (#1086)

* ci: add Lint check on commits

* ci: fix Lint script error

* test: fix go vet errors

* test: fix go vet errors, remove gofumpt to check go vet

* test: fix go vet errors, try gofumpt

* test: fix go vet errors, try gofumpt, round 1

* test: fix go vet errors, try gofumpt, round 2

* ci: fix Lint errors

core/discov/internal/statewatcher_mock.go

@@ -6,9 +6,10 @@ package internal
 
 import (
 	context "context"
+	reflect "reflect"
+
 	gomock "github.com/golang/mock/gomock"
 	connectivity "google.golang.org/grpc/connectivity"
-	reflect "reflect"
 )
 
 // MocketcdConn is a mock of etcdConn interface

core/discov/internal/updatelistener_mock.go

@@ -5,8 +5,9 @@
 package internal
 
 import (
-	gomock "github.com/golang/mock/gomock"
 	reflect "reflect"
+
+	gomock "github.com/golang/mock/gomock"
 )
 
 // MockUpdateListener is a mock of UpdateListener interface