e2e: remove existing replace lines in go.mod for the SDK repo (#1664) (#1719)

* hack/,test/e2e/memcached_test.go: remove existing replace lines in
go.mod for the SDK repo

Author: Eric Stroczynski

hack/lib/test_lib.sh

@@ -75,6 +75,10 @@ function add_go_mod_replace() {
 		echo "module ${from_path}" > "${to_path}/go.mod"
 		trap_add "rm ${to_path}/go.mod" EXIT
 	fi
+	# Check if a replace line already exists. If it does, remove. If not, append.
+	if grep -q "${from_path} =>" go.mod; then
+		sed -E -i 's|^.+'"${from_path} =>"'.+$||g' go.mod
+	fi
 	# Do not use "go mod edit" so formatting stays the same.
 	local replace="replace ${from_path} => ${to_path}"
 	if [[ -n "$version" ]]; then

test/e2e/memcached_test.go

@@ -22,6 +22,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"strings"
 	"testing"
 	"time"
@@ -126,7 +127,7 @@ func TestMemcached(t *testing.T) {
 				}()
 			}
 		}
-		modBytes, err := insertGoModReplace(t, sdkRepo, replace.repo, replace.ref)
+		modBytes, err := insertGoModReplace(sdkRepo, replace.repo, replace.ref)
 		if err != nil {
 			t.Fatalf("Failed to insert go.mod replace: %v", err)
 		}
@@ -311,11 +312,15 @@ func getGoModReplace(t *testing.T, localSDKPath string) goModReplace {
 	}
 }
 
-func insertGoModReplace(t *testing.T, repo, path, sha string) ([]byte, error) {
+func insertGoModReplace(repo, path, sha string) ([]byte, error) {
 	modBytes, err := ioutil.ReadFile("go.mod")
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to read go.mod")
 	}
+	// Remove all replace lines in go.mod.
+	replaceRe := regexp.MustCompile(fmt.Sprintf("(replace )?%s =>.+", repo))
+	modBytes = replaceRe.ReplaceAll(modBytes, nil)
+	// Append the desired replace to the end of go.mod's bytes.
 	sdkReplace := fmt.Sprintf("replace %s => %s", repo, path)
 	if sha != "" {
 		sdkReplace = fmt.Sprintf("%s %s", sdkReplace, sha)