Add Go example to read meta-data log.

examples/meta_log/go/main.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+
+	"github.com/chirpstack/chirpstack/api/go/v4/meta"
+	"github.com/go-redis/redis/v8"
+	"google.golang.org/protobuf/encoding/protojson"
+	"google.golang.org/protobuf/proto"
+)
+
+var (
+	server string
+	key    string
+)
+
+func init() {
+	flag.StringVar(&server, "server", "localhost:6379", "Redis hostname:port")
+	flag.StringVar(&key, "key", "stream:meta", "Redis Streams key to read from")
+	flag.Parse()
+}
+
+func main() {
+	rdb := redis.NewClient(&redis.Options{
+		Addr: server,
+	})
+	ctx := context.Background()
+
+	lastID := "0"
+
+	for {
+		resp, err := rdb.XRead(ctx, &redis.XReadArgs{
+			Streams: []string{key, lastID},
+			Count:   10,
+			Block:   0,
+		}).Result()
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		if len(resp) != 1 {
+			log.Fatal("Exactly one stream response is expected")
+		}
+
+		for _, msg := range resp[0].Messages {
+			lastID = msg.ID
+
+			if b, ok := msg.Values["up"].(string); ok {
+				var pl meta.UplinkMeta
+				if err := proto.Unmarshal([]byte(b), &pl); err != nil {
+					log.Fatal(err)
+				}
+
+				fmt.Println("=== UP ===")
+				fmt.Println(protojson.Format(&pl))
+				fmt.Println("==========")
+			}
+
+			if b, ok := msg.Values["down"].(string); ok {
+				var pl meta.DownlinkMeta
+				if err := proto.Unmarshal([]byte(b), &pl); err != nil {
+					log.Fatal(err)
+				}
+
+				fmt.Println("=== DOWN ===")
+				fmt.Println(protojson.Format(&pl))
+				fmt.Println("============")
+			}
+		}
+	}
+}