fix bug (DL4001 is too error lines) (#9)

linter/rules/dl4001.go

@@ -6,27 +6,28 @@ import (
 	"github.com/moby/buildkit/frontend/dockerfile/parser"
 )
 
-// validateDL4001 Either use Wget or Curl but not both
+// validateDL4001 is dockerfile linter DL4001 rule.
+// Either use Wget or Curl but not both.
 func validateDL4001(node *parser.Node) (rst []ValidateResult, err error) {
 	isCurl, isWget := false, false
-	var numArr []int
+	var lines []int
 	for _, child := range node.Children {
 		if child.Value == RUN {
 			for _, v := range strings.Fields(child.Next.Value) {
 				switch v {
 				case "curl":
 					isCurl = true
-					numArr = append(numArr, child.StartLine)
+					lines = append(lines, child.StartLine)
 				case "wget":
 					isWget = true
-					numArr = append(numArr, child.StartLine)
+					lines = append(lines, child.StartLine)
 				}
 			}
 		}
-		if isCurl && isWget {
-			for _, num := range numArr {
-				rst = append(rst, ValidateResult{line: num, addMsg: ""})
-			}
+	}
+	if isCurl && isWget {
+		for _, line := range lines {
+			rst = append(rst, ValidateResult{line: line, addMsg: ""})
 		}
 	}
 	return rst, nil