Rule for defering methods which return errors (#441)

testutils/source.go

@@ -1435,7 +1435,57 @@ func main() {
 	
 	d2 := []byte{115, 111, 109, 101, 10}
 	n2, err := f.Write(d2)
+
+	defer check(err)
+	fmt.Printf("wrote %d bytes\n", n2)
+	
+	n3, err := f.WriteString("writes\n")
+	fmt.Printf("wrote %d bytes\n", n3)
+	
+	f.Sync()
+	
+	w := bufio.NewWriter(f)
+	n4, err := w.WriteString("buffered\n")
+	fmt.Printf("wrote %d bytes\n", n4)
+	
+	w.Flush()
+
+}`}, 1, gosec.NewConfig()}}
+	// SampleCodeG307 - Unsafe defer of os.Close
+	SampleCodeG307 = []CodeSample{
+		{[]string{`package main
+
+import (
+	"bufio"
+	"fmt"
+	"io/ioutil"
+	"os"
+)
+
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+
+func main() {
+
+	d1 := []byte("hello\ngo\n")
+	err := ioutil.WriteFile("/tmp/dat1", d1, 0744)
 	check(err)
+
+	allowed := ioutil.WriteFile("/tmp/dat1", d1, 0600)
+	check(allowed)
+
+	f, err := os.Create("/tmp/dat2")
+	check(err)
+
+	defer f.Close()
+
+	d2 := []byte{115, 111, 109, 101, 10}
+	n2, err := f.Write(d2)
+
+	defer check(err)
 	fmt.Printf("wrote %d bytes\n", n2)
 	
 	n3, err := f.WriteString("writes\n")
@@ -1462,6 +1512,7 @@ import (
 	"log"
 	"os"
 )
+
 func main() {
 	f, err := os.Open("file.txt")
 	if err != nil {
@@ -1469,6 +1520,13 @@ func main() {
 	}
 	defer f.Close()
 
+	defer func() {
+	  err := f.Close()
+	  if err != nil {
+		 log.Printf("error closing the file: %s", err)
+	  }
+	}()
+
 	h := md5.New()
 	if _, err := io.Copy(h, f); err != nil {
 		log.Fatal(err)