golang switch type based on string key in map

I need to get a type based on a string key of types map. Suppose I have the following types:

type RequestType struct {
  Type string `json:"type"`
  //Params map[string]string `json:"params"`//include params here? Contents of Params may be different among requests
}

type ParamsRequest struct {
 RequestType
 Param1 string
 Param2 string
}

type OtherRequest struct {
  RequestType
  Param3 string
  Param4 string
}

Later on..

var requestTypes = map[string]protocol.RequestType{
  "base": ParamsRequest{}, //error here (Cannot use ParamsRequest as the type RequestType)
  "base2": OtherRequest{},
}

params := requestTypes["base"] //or base2

And in the code I need to access common fields for all request types:

myFunction(params.Type)//or params.Params 

Or params, specific for concrete type.
So:

params := requestTypes["base"]
fmt.Println(params.Type)//common for everyone
fmt.Println(params.Param1)
fmt.Println(params.Param2)

Or:

params := requestTypes["base2"]
fmt.Println(params.Type)
fmt.Println(params.Param3)
fmt.Println(params.Param4)

Or:

params := requestTypes["base"]
fmt.Println(params.Params.Param1)
fmt.Println(params.Params.Param2)

But instead when declaring my map I get the following error:

Cannot use ParamsRequest as the type RequestType

Any idea would be welcome. Thank you.

If I understand the requirement correctly here, you want to create an interface of RequestType which will be implemented by both the Request structs. below is a sample code for it.

package main

import "fmt"

type RequestType interface {
	Type() string // an interface with Type as a function
}
  
type ParamsRequest struct {
	Param1 string
	Param2 string
}
func (p ParamsRequest) Type() string { // different Type() logic for different Request types
	return fmt.Sprintf("%s,%s", p.Param1, p.Param2)
}
  
type OtherRequest struct {
	Param3 string
	Param4 string
}
func (o OtherRequest) Type() string {
	return fmt.Sprintf("%s,%s", o.Param3, o.Param4)
}

func main() {
	var requestTypes = map[string]RequestType{
		"base": ParamsRequest{Param1: "hi", Param2: "bye"}, //error here (Cannot use ParamsRequest as the type RequestType)
		"base2": OtherRequest{},
	}

	myFunction(requestTypes["base"].Type())
}

func myFunction(paramTypeString string) {
	fmt.Printf("%s\ndont know ...\n", paramTypeString)
}