Unmarshal GO YAML to either a Map or a String - go

Question

I'm trying to unmarshal YAML entries that can be either a string or a list of key: value strings (a map as per Go). I cannot figure out how to get this done sadly. I know I can write my own unmarshaller but that seems to only work with structs.
I have the first part working:
package main
import (
"log"
"gopkg.in/yaml.v2"
)
type Data struct {
Entry []Entry `yaml:"entries"`
}
type Entry map[string]string
var dat string = `
entries:
- keya1: val1
keya2: val2
- keyb1: val1
keyb2: val2
- val3`
func main() {
out := Data{}
if err := yaml.Unmarshal([]byte(dat), &out); err != nil {
log.Fatal(err)
}
log.Printf("%+v", out)
}
But the - val3 entry causes an error now, obviously. How can I get it to recognise both lists and single string entries?
Thank you

Answer 1

This is just a followup to the excellent #Benjamin Kadish answer above, but here's a somewhat more complete version and this uses yaml.v3, which makes it just a bit more obvious. Note that the type of the unmarshalled items is map[string]interface{} instead of map[interface{}]interface{} in yaml v3.
package main
import (
"gopkg.in/yaml.v3"
"log"
)
type Data struct {
Entry []Entry `yaml:"entries"`
}
type Entry interface {}
var dat string = `
entries:
- keya1: val1
keya2: val2
- keyb1: val1
keyb2: val2
- val3`
func main() {
out := Data{}
if err := yaml.Unmarshal([]byte(dat), &out); err != nil {
log.Fatal(err)
}
for _, entry := range out.Entry {
switch i := entry.(type) {
case string:
log.Printf("i is a string: %+v\n", i)
case map[string]interface{}:
log.Printf("i is a map.")
for k,v := range i {
log.Printf("%s=%v\n",k,v)
}
default:
log.Printf("Type i=%s", i)
}
}
}

Answer 2

This has been answered in various ways before, but long story short it is easy unmarshall into an interface and then deal with both cases
type Entry interface{}
for _, entry := range out.Entry {
switch i := entry.(type) {
case string:
log.Printf("i is a string %+v\n", i)
case map[interface{}]interface{}:
log.Printf("i is a map %+v\n", i)
}
}

Answer 3

As, go is static type language, you can't leave val3 only a list item if you convert it to defined struct. It should be key value pair. E.g. (val3: "") (if you want it empty.)
Here is modified code
package main
import (
"log"
"gopkg.in/yaml.v2"
)
type Data struct {
Entry []Entry `yaml:"entries"`
}
type Entry map[string]string
var dat string = `
entries:
- keya1: val1
keya2: val2
- keyb1: val1
keyb2: val2
- val3: ""`
func main() {
out := Data{}
if err := yaml.Unmarshal([]byte(dat), &out); err != nil {
log.Fatal(err)
}
log.Printf("%+v", out)
}
And output:
2018/02/02 01:07:36 {Entry:[map[keya1:val1 keya2:val2] map[keyb2:val2 keyb1:val1] map[val3:]]}