Sum numbers input from terminal
No sense send slice of numbers into the summation function. Would be better pass the string and work with it. This will avoid necessary  enumeration of the elements of the slice and return result.
No need to create a slice with 0 capacity,because it will increase costly. In your case, it was possible to write so:


floatsSlice := make([]float64, len(textSlice))
 ...
 for index, elem := range textSlice {
     ...
    floatsSlice[index] = i
 }   


No need to create extra variable

fmt.Println("Here is the result:", AddAll(ReadInput()))


Putting it all together and the result is:

func getline() (string, error) {
    return bufio.NewReader(os.Stdin).ReadString('\n')
}

func sumNumbers(str string) float64 {
    var sum float64
    for _, v := range strings.Fields(str) {
        i, err := strconv.ParseFloat(v, 64)
        if err != nil {
            fmt.Println(err)
        } else {
            sum += i
        }
    }
    return sum
}


Call:

str, err := getline()
if err == nil {
    fmt.Println("Here is the result:", sumNumbers(str))
}