Add GetHostPort function to extract the host and port from network addresses (#29)

This patch adds a new utility function called `GetHostPort` to help
extracting the host and port from network addresses.
This function will be used in the generated `main.go` to configure
the webhook server host and port. 

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Author: a-hilaly

pkg/util/address.go

@@ -0,0 +1,28 @@
+package util
+
+import (
+	"fmt"
+	"net"
+	"net/url"
+	"strconv"
+)
+
+// GetHostPort extracts the host and port from a given address string.
+func GetHostPort(address string) (string, int, error) {
+	u, err := url.Parse(fmt.Sprintf("//%s", address))
+	if err != nil {
+		return "", 0, err
+	}
+
+	host, portString, err := net.SplitHostPort(u.Host)
+	if err != nil {
+		return "", 0, err
+	}
+
+	port, err := strconv.Atoi(portString)
+	if err != nil {
+		return "", 0, fmt.Errorf("cannot parse port: %v", err)
+	}
+
+	return host, port, nil
+}

pkg/util/address_test.go

@@ -0,0 +1,87 @@
+package util_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/aws-controllers-k8s/runtime/pkg/util"
+)
+
+func TestGetHostPort(t *testing.T) {
+	assert := assert.New(t)
+	type args struct {
+		address string
+	}
+	testCases := []struct {
+		name     string
+		args     args
+		wantErr  bool
+		wantHost string
+		wantPort int
+	}{
+		{
+			name: "empty string",
+			args: args{
+				address: "",
+			},
+			wantErr: true,
+		},
+		{
+			name: "malformed address",
+			args: args{
+				address: "host::1",
+			},
+			wantErr: true,
+		},
+		{
+			name: "port only",
+			args: args{
+				address: ":500",
+			},
+			wantErr:  false,
+			wantHost: "",
+			wantPort: 500,
+		},
+		{
+			name: "host only - port should be specified",
+			args: args{
+				address: "localhost",
+			},
+			wantErr: true,
+		},
+		{
+			name: "ipv4",
+			args: args{
+				address: "0.0.0.0:80",
+			},
+			wantErr:  false,
+			wantHost: "0.0.0.0",
+			wantPort: 80,
+		},
+		{
+			name: "ipv6",
+			args: args{
+				address: "[0::0]:443",
+			},
+			wantErr:  false,
+			wantHost: "0::0",
+			wantPort: 443,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			host, port, err := util.GetHostPort(
+				tc.args.address,
+			)
+			if (err != nil) != tc.wantErr {
+				assert.Fail(fmt.Sprintf("GetHostPort(%s) error = %v, wantErr %v", tc.name, err, tc.wantErr))
+			} else if !tc.wantErr {
+				assert.Equal(tc.wantHost, host)
+				assert.Equal(tc.wantPort, port)
+			}
+		})
+	}
+}