how to return struct

func returnStruct{
        syscall_ptr : felt*,
        pedersen_ptr : HashBuiltin*,
        range_check_ptr
    }(_id : felt) -> (res: ExampleStruct):
    let (res) = _example_structs.read(_id )
    return (res)
end

or

func returnStruct{
        syscall_ptr : felt*,
        pedersen_ptr : HashBuiltin*,
        range_check_ptr
    }() -> (res: ExampleStruct):
    let (res) = ExampleStruct(a=1,b=2)
    return (res)
end

I highly recommend you return a pointer to struct like this:

struct MyStruct{
    a: felt*,
    b: felt,
}

func my_func() -> (output: MyStruct*){
}