cmd/go: add two more uses of lazyregexp

A couple of regexp.MustCompile globals have made their way in since we
introduced this package for cmd/go.

Convert the declarations. It's just two of them, so the cmd/go exec
benchmark isn't affected noticeably.

Change-Id: Ibd0615c99b6a049124a952c59978fd714c1b9615
Reviewed-on: https://go-review.googlesource.com/c/go/+/179358
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/internal/modconv/dep.go

@@ -6,9 +6,9 @@ package modconv
 
 import (
 	"fmt"
+	"internal/lazyregexp"
 	"net/url"
 	"path"
-	"regexp"
 	"strconv"
 	"strings"
 
@@ -96,7 +96,7 @@ func ParseGopkgLock(file string, data []byte) (*modfile.File, error) {
 	return mf, nil
 }
 
-var scpSyntaxReg = regexp.MustCompile(`^([a-zA-Z0-9_]+)@([a-zA-Z0-9._-]+):(.*)$`)
+var scpSyntaxReg = lazyregexp.New(`^([a-zA-Z0-9_]+)@([a-zA-Z0-9._-]+):(.*)$`)
 
 func decodeSource(source string) (string, error) {
 	var u *url.URL

src/cmd/go/internal/sumweb/server.go

@@ -7,9 +7,9 @@ package sumweb
 
 import (
 	"context"
+	"internal/lazyregexp"
 	"net/http"
 	"os"
-	"regexp"
 	"strings"
 
 	"cmd/go/internal/tlog"
@@ -59,7 +59,7 @@ var Paths = []string{
 	"/tile/",
 }
 
-var modVerRE = regexp.MustCompile(`^[^@]+@v[0-9]+\.[0-9]+\.[0-9]+(-[^@]*)?(\+incompatible)?$`)
+var modVerRE = lazyregexp.New(`^[^@]+@v[0-9]+\.[0-9]+\.[0-9]+(-[^@]*)?(\+incompatible)?$`)
 
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	ctx, err := h.Server.NewContext(r)