GO语言菜鸟-问题

const result = "Polar radius =%.02f θ=%.02f° →Cartesian x = %.02f  y =%.02f\n"

func interact(questions chan polar, answers chan cartesian) {
   reader := bufio.NewReader(os.Stdin)
   fmt.Println(prompt)

   for{
    fmt.Println("Radius  and angle:")
    line, err:= reader.ReadString('\n')
    if  err != nil{
      break
    }


    var radius,θ  float64
    if _,err:= fmt.Sscan(line, "%f %f ",&radius,&θ);  err != nil {
    fmt.Println(os.Stderr, "invalid input")
    fmt.Println("err=",err)
     continue
    }

    questions <-polar{radius,θ}
    coord := <-answers
    fmt.Println(result, radius,θ,coord.x,coord.y )
   }

   fmt.Println()
}

编译执行时，在如下代码报错：

var radius,θ  float64
if _,err:= fmt.Sscan(line, "%f %f ",&radius,&θ);  err != nil {
fmt.Println(os.Stderr, "invalid input")
fmt.Println("err=",err)
 continue
}

错误信息：

&{0xc42000a3a0} invalid input
err= type not a pointer: string
Radius  and angle:

请大神指点