fix: removed dependency on pkg/errors in tests

Signed-off-by: Martin Chodur <m.chodur@seznam.cz>

go.mod

@@ -2,7 +2,6 @@ module github.com/grpc-ecosystem/go-grpc-prometheus
 
 require (
 	github.com/golang/protobuf v1.2.0
-	github.com/pkg/errors v0.8.1
 	github.com/prometheus/client_golang v0.9.2
 	github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90
 	github.com/stretchr/testify v1.3.0

go.sum

@@ -12,8 +12,6 @@ github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5y
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/matttproud/golang_protobuf_extensions v1.0.1 h1:4hp9jkHxhMHkqkrB3Ix0jegS5sx/RkqARlsWZ6pIwiU=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
-github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
-github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_golang v0.9.2 h1:awm861/B8OKDd2I/6o1dy3ra4BamzKhYOiGItCeZ740=

server_test.go

@@ -7,7 +7,6 @@ import (
 	"bufio"
 	"context"
 	"fmt"
-	"github.com/pkg/errors"
 	"io"
 	"net"
 	"net/http"
@@ -252,11 +251,22 @@ func (s *testService) Ping(ctx context.Context, ping *pb_testproto.PingRequest)
 	return &pb_testproto.PingResponse{Value: ping.Value, Counter: 42}, nil
 }
 
+
+// Own implementation of pkg/errors withStack to avoid additional dependency
+type wrappedError struct {
+	cause error
+	msg string
+}
+
+func (w *wrappedError) Error() string { return w.msg + ": " + w.cause.Error() }
+
+func (w *wrappedError) Cause() error { return w.cause }
+
 func (s *testService) PingError(ctx context.Context, ping *pb_testproto.PingRequest) (*pb_testproto.Empty, error) {
 	code := codes.Code(ping.ErrorCodeReturned)
 	err := status.Errorf(code, "Userspace error.")
 	if ping.Value == "wrapf" {
-		err = errors.Wrapf(err, "wrapped error")
+		err = &wrappedError{cause: err}
 	}
 	//if ping.Value == "errorf" {
 	//	err = fmt.Errorf("wrapped error: %w", err)