fix: replace panic with log.Fatal in grpc-smoke-client

Use idiomatic log.Fatal/log.Fatalf instead of panic for CLI error
handling in the smoke test tool.

Author: mahmut-Abi

cmd/grpc-smoke-client/main.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"log"
 	"math"
 	"os"
 	"sort"
@@ -59,10 +60,10 @@ func main() {
 	flag.Parse()
 
 	if *requests < 1 {
-		panic("requests must be >= 1")
+		log.Fatal("requests must be >= 1")
 	}
 	if *concurrency < 1 {
-		panic("concurrency must be >= 1")
+		log.Fatal("concurrency must be >= 1")
 	}
 
 	conn, err := grpc.NewClient(
@@ -71,7 +72,7 @@ func main() {
 		grpc.WithAuthority(*authority),
 	)
 	if err != nil {
-		panic(fmt.Errorf("create grpc client: %w", err))
+		log.Fatalf("create grpc client: %v", err)
 	}
 	defer conn.Close()
 
@@ -80,14 +81,14 @@ func main() {
 
 	if !*jsonOutput && *requests == 1 && *concurrency == 1 {
 		if summary.Successes != 1 {
-			panic(fmt.Errorf("invoke grpc method %s via %s: %s", *method, *addr, results[0].Error))
+			log.Fatalf("invoke grpc method %s via %s: %s", *method, *addr, results[0].Error)
 		}
 		fmt.Println("grpc smoke ok")
 		return
 	}
 
 	if err := json.NewEncoder(os.Stdout).Encode(summary); err != nil {
-		panic(fmt.Errorf("encode summary: %w", err))
+		log.Fatalf("encode summary: %v", err)
 	}
 
 	if summary.Successes != summary.Completed {