Example: Create a basic example to start with Toxics

Real life working example to create a new toxic.
Add readme to show how to test toxics.

Author: miry

examples/toxics/README.md

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+# Examples
+
+Example how to start building own toxics.
+
+Run custom toxiserver with DebugToxic.
+
+```shell
+$ go run debug_toxic.go
+```
+
+Run redis-server in separate terminal:
+
+```shell
+$ redis-server
+```
+
+Test toxic with:
+
+```shell
+$ toxiproxy-cli --host "http://localhost:8484" create -l :16379 -u localhost:6379 redis
+$ toxiproxy-cli --host "http://localhost:8484" t add --type debug redis
+$ redis-cli -p 16379 "keys" "*"
+```
+
+Custom Toxiproxy should print bytes in hex format.

examples/toxics/debug_toxic.go

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+package main
+
+import (
+	"os"
+	"log"
+	"fmt"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/rs/zerolog"
+
+	"github.com/Shopify/toxiproxy/v2"
+	"github.com/Shopify/toxiproxy/v2/toxics"
+)
+
+// DebugToxic prints bytes processed through pipe.
+type DebugToxic struct{}
+
+func (t *DebugToxic) PrintHex(data []byte) {
+	for i := 0; i < len(data); {
+		for j := 0; j < 4; j +=1 {
+			x := i + 8
+			if x >= len(data) {
+				x = len(data) - 1
+				fmt.Printf("% x\n", data[i:x])
+				return
+			}
+			fmt.Printf("% x\t\t", data[i:x])
+			i = x
+		}
+		fmt.Println()
+	}
+}
+
+func (t *DebugToxic) Pipe(stub *toxics.ToxicStub) {
+	for {
+		select {
+		case <-stub.Interrupt:
+			return
+		case c := <-stub.Input:
+			if c == nil {
+				stub.Close()
+				return
+			}
+			log.Printf("-- [DebugToxic] Processed %d bytes\n", len(c.Data))
+			t.PrintHex(c.Data)
+			stub.Output <- c
+		}
+	}
+}
+
+func main() {
+	toxics.Register("debug", new(DebugToxic))
+
+	logger := zerolog.New(os.Stderr).With().Caller().Timestamp().Logger()
+	metrics := toxiproxy.NewMetricsContainer(prometheus.NewRegistry())
+	server := toxiproxy.NewServer(metrics, logger)
+	server.Listen("0.0.0.0:8484")
+}