Improve the G307 rule

* Add G307 sample code.
The sample should reflect a defered close that leads to data loss.
Due to IDE auto-complete people tend at least log errors, but not
really care about handling.

* Add more G307 sample code. Propose a way to implement

* Remove unused code. Add example that should not return an error but does

* Remove test for synced closed file for now.
Will add this later

Co-authored-by: Cosmin Cojocar <cosmin.cojocar@gmx.ch>

testutils/source.go

@@ -1984,7 +1984,6 @@ func main() {
 		{[]string{`package main
 
 import (
-	"bufio"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -2016,16 +2015,86 @@ func main() {
 	defer check(err)
 	fmt.Printf("wrote %d bytes\n", n2)
 
-	n3, err := f.WriteString("writes\n")
-	fmt.Printf("wrote %d bytes\n", n3)
+}`}, 1, gosec.NewConfig()},
+		{[]string{`package main
 
-	f.Sync()
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+)
 
-	w := bufio.NewWriter(f)
-	n4, err := w.WriteString("buffered\n")
-	fmt.Printf("wrote %d bytes\n", n4)
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
 
-	w.Flush()
+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 func() {
+		if err := f.Close(); err != nil {
+			log.Println(err)
+		}
+	}()
+
+	d2 := []byte{115, 111, 109, 101, 10}
+	n2, err := f.Write(d2)
+
+	defer check(err)
+	fmt.Printf("wrote %d bytes\n", n2)
+
+}`}, 1, gosec.NewConfig()},
+		{[]string{`package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"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 func() {
+		err := f.Close()
+		if err != nil {
+			log.Println(err)
+		}
+	}()
+
+	d2 := []byte{115, 111, 109, 101, 10}
+	n2, err := f.Write(d2)
+
+	defer check(err)
+	fmt.Printf("wrote %d bytes\n", n2)
 
 }`}, 1, gosec.NewConfig()},
 	}