Elapsed time in JSON output (#61)

* Add ElapsedTime to JSON output

Add the ElapsedTime to the JSON output and expose the tcp:// method in the documentation

* Run go fmt

* Address comment from ameshkov

Instead of manipulating JSON strings, load the data into a variable with an extended type and then marshal the variable

* Fix lint error

un-export JSONMsg type

README.md

@@ -5,7 +5,7 @@
 # dnslookup
 
 Simple command line utility to make DNS lookups. Supports all known DNS
-protocols: plain DNS, DoH, DoT, DoQ, DNSCrypt.
+protocols: plain DNS, plain DNS-over-TCP, DoH, DoT, DoQ, DNSCrypt.
 
 ### How to install
 
@@ -35,6 +35,12 @@ Plain DNS:
 dnslookup example.org 94.140.14.14
 ```
 
+Plain DNS-over-TCP:
+
+```shell
+dnslookup example.org tcp://94.140.14.14
+```
+
 DNS-over-TLS:
 
 ```shell

main.go

@@ -19,6 +19,11 @@ import (
 	"github.com/miekg/dns"
 )
 
+type jsonMsg struct {
+	dns.Msg
+	Elapsed time.Duration `json:"elapsed"`
+}
+
 // VersionString -- see the makefile
 var VersionString = "master"
 
@@ -171,8 +176,15 @@ func main() {
 		os.Stdout.WriteString(msg)
 		os.Stdout.WriteString(reply.String() + "\n")
 	} else {
+		// Prevent JSON parsing from skewing results
+		endTime := time.Now()
+
+		var JSONreply jsonMsg
+		JSONreply.Msg = *reply
+		JSONreply.Elapsed = endTime.Sub(startTime)
+
 		var b []byte
-		b, err = json.MarshalIndent(reply, "", "  ")
+		b, err = json.MarshalIndent(JSONreply, "", "  ")
 		if err != nil {
 			log.Fatalf("Cannot marshal json: %s", err)
 		}
@@ -285,7 +297,7 @@ func getRRType() (rrType uint16) {
 func usage() {
 	os.Stdout.WriteString("Usage: dnslookup <domain> <server> [<providerName> <serverPk>]\n")
 	os.Stdout.WriteString("<domain>: mandatory, domain name to lookup\n")
-	os.Stdout.WriteString("<server>: mandatory, server address. Supported: plain, tls:// (DOT), https:// (DOH), sdns:// (DNSCrypt), quic:// (DOQ)\n")
+	os.Stdout.WriteString("<server>: mandatory, server address. Supported: plain, tcp:// (TCP), tls:// (DOT), https:// (DOH), sdns:// (DNSCrypt), quic:// (DOQ)\n")
 	os.Stdout.WriteString("<providerName>: optional, DNSCrypt provider name\n")
 	os.Stdout.WriteString("<serverPk>: optional, DNSCrypt server public key\n")
 }