error prone way of iterating through go struct tags as a map[string]string data structure in golang

struct_field_tags.go

package main

import (
	"fmt"
	"reflect"
	"strings"

	".../model"
)

func main() {
	m := model.Topic{}
	mv := reflect.ValueOf(m)
	mt := mv.Type()
  fmt.Printf("%v: %v\n", mt.Name(), mt)
	for i := 0; i < mt.NumField(); i++ {
		f := mt.Field(i)
    fmt.Printf("\t%v: %v\n", f.Name, f.Type)
		tags, err := GetTags(f.Tag)
		if err != nil {
			panic(err)
		}
    for k, v := range tags {
      fmt.Printf("\t\t%s: %v\n", k, v)
    }
	}
}

func GetTags(tag reflect.StructTag) (map[string]string, error) {
  t := string(tag)
	ret := make(map[string]string)
	for {
		// Find single next key value pair in tag.
		b := strings.Index(t, `:`)
		if b == -1 {
			break
		}
		a := 1 + strings.LastIndex(t[:b], ` `)

		// Verify key value pair in tag.
		// Wish go had something like this builtin to iterate over tags like a
		// map...
		k := t[a:b]
		v, ok := tag.Lookup(k)
		if !ok {
			panic(fmt.Sprintf("key %v doesn't exist in tag: %v", k, tag))
		}
    ret[k] = v

		// Next
		t = strings.TrimSpace(t[b+1:])
	}
  return ret, nil
}