snake case a camel cased word in Go

utils.go

package utils                                                                                                                                                                                                                                                                                                                                                                         

import (                                                                                                                                                                                                                                                                                                                                                                              
  "strings"                                                                                                                                                                                                                                                                                                                                                                           
  "unicode"                                                                                                                                                                                                                                                                                                                                                                           
)                                                                                                                                                                                                                                                                                                                                                                                     

func SnakeCase(str string) string {                                                                                                                                                                                                                                                                                                                                                   
  var words []string                                                                                                                                                                                                                                                                                                                                                                  
  l := 0                                                                                                                                                                                                                                                                                                                                                                              

  for s := str; s != ""; s = s[l:] {                                                                                                                                                                                                                                                                                                                                                  
    l = strings.IndexFunc(s[1:], unicode.IsUpper) + 1                                                                                                                                                                                                                                                                                                                                 
    if l <= 0 {                                                                                                                                                                                                                                                                                                                                                                       
      l = len(s)                                                                                                                                                                                                                                                                                                                                                                      
    }                                                                                                                                                                                                                                                                                                                                                                                 
    words = append(words, s[:l])                                                                                                                                                                                                                                                                                                                                                      
  }                                                                                                                                                                                                                                                                                                                                                                                   
  snaked := strings.Join(words, "_")                                                                                                                                                                                                                                                                                                                                                   
  snaked = strings.ToLower(snaked)                                                                                                                                                                                                                                                                                                                                                    
  return snaked                                                                                                                                                                                                                                                                                                                                                                       
}