For example, this FindDigits function loads a file into memory and searches it for the first group of consecutive numeric digits, returning them as a new slice. ``` var digitRegexp = regexp.MustCompile("[0-9]+")
func FindDigits(filename string) []byte {
b, _ := ioutil.ReadFile(filename)
return digitRegexp.Find(b)
}
This code behaves as advertised, but the returned []byte points into an array containing the entire file. Since the slice references the original array, as long as the slice is kept around the garbage collector can’t release the array; the few useful bytes of the file keep the entire contents in memory.
To fix this problem one can copy the interesting data to a new slice before returning it:
func CopyDigits(filename string) []byte {
b, _ := ioutil.ReadFile(filename)
b = digitRegexp.Find(b)
c := make([]byte, len(b))
copy(c, b)
return c
}
```