filter1.go and butter.go usage question

[boksili]

I am so real real New in GOLANG.
I try to use you code for butterworth 1st order highpass filter for DSP.
I want ask the code using method for your code

I coded like

package main
import (
"github.com/jfcg/butter"
}
func main() {
signal1, err := dsp.ReadSignalFile("./signal.txt', 0.016666) //1 column data for water well height recoded each 60 seconds
if err !=nil {
panic(err)
}

       signal2 := butter.NewHighPass1(0.005, signal1)

---

so, I did fmt.Println("signal2: ", signal2.Signal[0:10])
but failed.
the error massage replys,

signal2.Signal undefined (type butter.Filter has no field or method Signal)