Returns a string by concatenating all of the elements in the collection, separated by the specified separator string.

Use reflect.ValueOf() to get the array or slice and the separator string, make() to create an appropriate string slice.
Use a for loop with Value.Len() and Value.Index() to iterate over each element, fmt.Sprintf() to convert it to a string.
Use strings.Join() to combine the strings using the separator provided.

代码实现

import (
    "fmt"
    "reflect"
    "strings"
)

func Join(params ...interface{}) string {
    arr, sp := reflect.ValueOf(params[0]),
        reflect.ValueOf(params[1]).String()
    ars := make([]string, arr.Len())

    for i := 0; i < arr.Len(); i++ {
        ars[i] = fmt.Sprintf("%v", arr.Index(i))
    }

    return strings.Join(ars, sp)

}

使用样例

Join([]int{1, 2, 3}, ".") // "1.2.3"