ip/resolver/http/service.go: refactor default decoder function into its own module

ip/resolver/http/service.go

@@ -1,15 +1,14 @@
 package http
 
 import (
-	"bufio"
 	"context"
 	"io"
 	"net"
 	"net/http"
-	"strings"
 
 	httputils "dnsupdater/http"
 	"dnsupdater/ip/internal"
+	"dnsupdater/ip/resolver/decoder"
 )
 
 type Decoder func(io.Reader) (string, error)
@@ -32,14 +31,7 @@ func (s Service) Lookup(ctx context.Context) (net.IP, error) {
 	}
 
 	if s.Decoder == nil {
-		s.Decoder = func(r io.Reader) (string, error) {
-			line, err := bufio.NewReader(r).ReadString('\n')
-			if err == nil || err == io.EOF {
-				line = strings.TrimRight(line, "\r\n")
-				line = strings.TrimSpace(line)
-			}
-			return line, err
-		}
+		s.Decoder = decoder.Text
 	}
 
 	body, err := s.Decoder(resp.Body)