refactor: replace deprecated grpc.Dial with grpc.NewClient in code and docs

docs/GRPC.md

@@ -229,7 +229,7 @@ protoc --go_out=. --go-grpc_out=. protoapi.proto
 
 * **원격 서비스 클라이언트 기동 (`NewIoTServiceClient`)**:
   ```go
-  conn, _ := grpc.Dial(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
+  conn, _ := grpc.NewClient(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
   client := protoapi.NewIoTServiceClient(conn)
   ```
   서버와의 TCP 채널(`conn`)을 평문 전송(insecure) 기반으로 바인딩한 뒤, 해당 채널을 통해 원격 서비스를 호출할 수 있는 전송용 클라이언트 인스턴스를 확보합니다.

examples/grpcentity/client.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"grpccanary/examples/grpcentity/protoapi"
 	"math/rand"
-	"time"
 
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
@@ -39,9 +38,9 @@ func AskUpdateSensingData(ctx context.Context, m protoapi.IoTServiceClient, devi
 }
 
 func ClientRun(addr string) {
-	conn, err := grpc.Dial(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	conn, err := grpc.NewClient(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	if err != nil {
-		fmt.Println("Dial:", err)
+		fmt.Println("NewClient error:", err)
 		return
 	}
 
@@ -53,7 +52,6 @@ func ClientRun(addr string) {
 	}
 	fmt.Println("Server Date and Time:", r.Value)
 
-	rand.Seed(time.Now().Unix())
 	length := int64(rand.Intn(20))
 	p, err := AskPass(context.Background(), client, 100, length+1)
 	if err != nil {

examples/grpcentity/server.go

@@ -33,13 +33,13 @@ func random(min, max int, src rand.Source) int {
 // 	return min + int(v.Uint64())
 // }
 
-func getString(len int64) string {
+func getString(len int64, src rand.Source) string {
 	temp := ""
 	startChar := "!"
 	var i int64 = 1
 	for {
 		// For getting valid ASCII characters
-		myRand := random(0, 94, rand.NewSource(time.Now().UnixNano()))
+		myRand := random(0, 94, src)
 		newChar := string(startChar[0] + byte(myRand))
 		temp = temp + newChar
 		if i == len {
@@ -75,8 +75,8 @@ func (IoTServer) UpdateSensingData(ctx context.Context, r *protoapi.SensingData)
 }
 
 func (IoTServer) GetRandomPass(ctx context.Context, r *protoapi.RequestPass) (*protoapi.RandomPass, error) {
-	rand.Seed(r.GetSeed())
-	temp := getString(r.GetLength())
+	src := rand.NewSource(r.GetSeed())
+	temp := getString(r.GetLength(), src)
 
 	response := &protoapi.RandomPass{
 		Password: temp,