Update sample code, README, and circle v2 (#42)

Update sample code, README, and circle v2

.circleci/config.yml

+version: 2.0
+jobs:
+  build:
+    docker:
+      - image: circleci/golang:1.11
+    working_directory: /go/src/github.com/sparrc/go-ping
+    steps:
+      - checkout
+      - run:
+          name: Build and run some basic tests
+          command: |
+            go get ./...
+            go build -race -o ping_linux ./cmd/ping/ping.go
+            sudo ./ping_linux --privileged -c 2 www.google.com
+            sudo ./ping_linux --privileged -c 3 -i 200ms www.google.com
+            sudo ./ping_linux --privileged -c 10 -i 100ms -t 1s www.google.com
+            GOOS=darwin go build -o ping_darwin ./cmd/ping/ping.go
+      - store_artifacts:
+          path: ./ping_linux
+      - store_artifacts:
+          path: ./ping_darwin

README.md

@@ -25,6 +25,15 @@ if err != nil {
         panic(err)
 }
 
+// listen for ctrl-C signal
+c := make(chan os.Signal, 1)
+signal.Notify(c, os.Interrupt)
+go func() {
+	for _ = range c {
+		pinger.Stop()
+	}
+}()
+
 pinger.OnRecv = func(pkt *ping.Packet) {
         fmt.Printf("%d bytes from %s: icmp_seq=%d time=%v\n",
                 pkt.Nbytes, pkt.IPAddr, pkt.Seq, pkt.Rtt)
@@ -75,13 +84,19 @@ use setcap to allow your binary using go-ping to bind to raw sockets
 (or just run as super-user):
 
 ```
-setcap cap_net_raw=+ep /bin/goping-binary
+setcap cap_net_raw=+ep /bin/go-ping
 ```
 
+See [this blog](https://sturmflut.github.io/linux/ubuntu/2015/01/17/unprivileged-icmp-sockets-on-linux/)
+and [the Go icmp library](https://godoc.org/golang.org/x/net/icmp) for more details.
+
 ## Note on Windows Support:
 
-You have to use "SetPrivileged(true)" like "pinger.SetPrivileged(true)", otherwise you will receive an error:
-"Error listening for ICMP packets: socket: The requested protocol has not been configured into the system, or no implementation for it exists." This even works without admin privileges. Tested on Windows 10
+You must use `pinger.SetPrivileged(true)`, otherwise you will receive an error:
+
+```
+Error listening for ICMP packets: socket: The requested protocol has not been configured into the system, or no implementation for it exists.
+```
+
+This should without admin privileges. Tested on Windows 10.
 
-See [this blog](https://sturmflut.github.io/linux/ubuntu/2015/01/17/unprivileged-icmp-sockets-on-linux/)
-and [the Go icmp library](https://godoc.org/golang.org/x/net/icmp) for more details.

circle.yml

-test:
-  post:
-    - go build -race -o ping_linux ./cmd/ping/ping.go
-    - sudo ./ping_linux --privileged -c 2 www.google.com
-    - sudo ./ping_linux --privileged -c 3 -i 200ms www.google.com
-    - sudo ./ping_linux --privileged -c 10 -i 100ms -t 1s www.google.com
-    - GOOS=darwin go build -o ping_darwin ./cmd/ping/ping.go
-    - mv ping_linux $CIRCLE_ARTIFACTS
-    - mv ping_darwin $CIRCLE_ARTIFACTS

cmd/ping/ping.go

@@ -3,6 +3,8 @@ package main
 import (
 	"flag"
 	"fmt"
+	"os"
+	"os/signal"
 	"time"
 
 	"github.com/sparrc/go-ping"
@@ -53,6 +55,15 @@ func main() {
 		return
 	}
 
+	// listen for ctrl-C signal
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, os.Interrupt)
+	go func() {
+		for _ = range c {
+			pinger.Stop()
+		}
+	}()
+
 	pinger.OnRecv = func(pkt *ping.Packet) {
 		fmt.Printf("%d bytes from %s: icmp_seq=%d time=%v\n",
 			pkt.Nbytes, pkt.IPAddr, pkt.Seq, pkt.Rtt)