net/url: add tests for URLHostname

These changes add tests for URLHostname.

Change-Id: Ie474516401a2236a9be65fb5c4e478322b1a199c
GitHub-Last-Rev: 18f2d597be960c4d13cde12fef5d115926bff7bd
GitHub-Pull-Request: golang/go#31832
Reviewed-on: https://go-review.googlesource.com/c/go/+/175142Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/url/url_test.go

@@ -1634,6 +1634,12 @@ func TestURLHostname(t *testing.T) {
 		{"[1:2:3:4]", "1:2:3:4"},
 		{"[1:2:3:4]:80", "1:2:3:4"},
 		{"[::1]:80", "::1"},
+		{"[::1]", "::1"},
+		{"localhost", "localhost"},
+		{"localhost:443", "localhost"},
+		{"some.super.long.domain.example.org:8080", "some.super.long.domain.example.org"},
+		{"[2001:0db8:85a3:0000:0000:8a2e:0370:7334]:17000", "2001:0db8:85a3:0000:0000:8a2e:0370:7334"},
+		{"[2001:0db8:85a3:0000:0000:8a2e:0370:7334]", "2001:0db8:85a3:0000:0000:8a2e:0370:7334"},
 	}
 	for _, tt := range tests {
 		u := &URL{Host: tt.host}