upgrade go version to go 1.19 (#155)

go.mod

@@ -1,11 +1,22 @@
 module github.com/dgraph-io/dgo/v210
 
-go 1.12
+go 1.19
 
 require (
 	github.com/gogo/protobuf v1.3.2
 	github.com/pkg/errors v0.8.1
 	github.com/stretchr/testify v1.4.0
 	google.golang.org/grpc v1.27.0
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/golang/protobuf v1.4.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/net v0.0.0-20201021035429-f5854403a974 // indirect
+	golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f // indirect
+	golang.org/x/text v0.3.3 // indirect
+	google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013 // indirect
 	google.golang.org/protobuf v1.25.0 // indirect
+	gopkg.in/yaml.v2 v2.2.2 // indirect
 )