code: func (s Int64Slice) Search(x int64) int {
  	return sort.Search(len(s), func(i int) bool {
  		return s[i] >= x
  	})
  }
docs: // Search will search this slice and return an index that corresponds
  // to the lowest position of that value.  You'll need to check
  // separately if the value at that position is equal to x.  The
  // behavior of this method is undefinited if the slice is not sorted.