provide a timeout on http client

When using the `rqlite` CLI, I was unable to determine an issue of connection.
It turns out that the arugments I had provided were not working.
The issue did not present itself till I added a timeout to the HTTP client.

cmd/rqlite/main.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/Bowery/prompt"
 	"github.com/mkideal/cli"
+	clix "github.com/mkideal/cli/ext"
 	"github.com/rqlite/rqlite/cmd"
 	"github.com/rqlite/rqlite/cmd/rqlite/history"
 	httpcl "github.com/rqlite/rqlite/cmd/rqlite/http"
@@ -34,15 +35,16 @@ type Nodes map[string]Node
 
 type argT struct {
 	cli.Helper
-	Alternatives string `cli:"a,alternatives" usage:"comma separated list of 'host:port' pairs to use as fallback"`
-	Protocol     string `cli:"s,scheme" usage:"protocol scheme (http or https)" dft:"http"`
-	Host         string `cli:"H,host" usage:"rqlited host address" dft:"127.0.0.1"`
-	Port         uint16 `cli:"p,port" usage:"rqlited host port" dft:"4001"`
-	Prefix       string `cli:"P,prefix" usage:"rqlited HTTP URL prefix" dft:"/"`
-	Insecure     bool   `cli:"i,insecure" usage:"do not verify rqlited HTTPS certificate" dft:"false"`
-	CACert       string `cli:"c,ca-cert" usage:"path to trusted X.509 root CA certificate"`
-	Credentials  string `cli:"u,user" usage:"set basic auth credentials in form username:password"`
-	Version      bool   `cli:"v,version" usage:"display CLI version"`
+	Alternatives string        `cli:"a,alternatives" usage:"comma separated list of 'host:port' pairs to use as fallback"`
+	Protocol     string        `cli:"s,scheme" usage:"protocol scheme (http or https)" dft:"http"`
+	Host         string        `cli:"H,host" usage:"rqlited host address" dft:"127.0.0.1"`
+	Port         uint16        `cli:"p,port" usage:"rqlited host port" dft:"4001"`
+	Prefix       string        `cli:"P,prefix" usage:"rqlited HTTP URL prefix" dft:"/"`
+	Insecure     bool          `cli:"i,insecure" usage:"do not verify rqlited HTTPS certificate" dft:"false"`
+	CACert       string        `cli:"c,ca-cert" usage:"path to trusted X.509 root CA certificate"`
+	Credentials  string        `cli:"u,user" usage:"set basic auth credentials in form username:password"`
+	Version      bool          `cli:"v,version" usage:"display CLI version"`
+	HTTPTimeout  clix.Duration `cli:"t,http-timeout" usage:"set timeout on HTTP requests" dft:"30s"`
 }
 
 var cliHelp = []string{
@@ -394,10 +396,13 @@ func getHTTPClient(argv *argT) (*http.Client, error) {
 		}
 	}
 
-	client := http.Client{Transport: &http.Transport{
-		TLSClientConfig: &tls.Config{InsecureSkipVerify: argv.Insecure, RootCAs: rootCAs},
-		Proxy:           http.ProxyFromEnvironment,
-	}}
+	client := http.Client{
+		Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{InsecureSkipVerify: argv.Insecure, RootCAs: rootCAs},
+			Proxy:           http.ProxyFromEnvironment,
+		},
+		Timeout: argv.HTTPTimeout.Duration,
+	}
 
 	// Explicitly handle redirects.
 	client.CheckRedirect = func(req *http.Request, via []*http.Request) error {