I can't pass a delphi string as a parameter to a cgo dll - go

Question

I have a DLL compiled in Go as a c-shared lib that takes in a string as a parameter. It works fine in other languages, like Java, and Python using ctypes to simulate a c-string.
But, when trying to use this DLL in Delphi, I can't pass in a string as a parameter.
This is the function declaration in Go:
//export RequestCertificate
func RequestCertificate(jsonString string) *C.char{
log.Println("String: ", jsonString)`
In Python, I declared a structure that simulates a c-string like this:
class GoString(Structure):
_fields_ = [("chars", c_char_p), ("length", c_longlong)]
And then passed this structure as a parameter:
jsonStr = json.dumps(payload)
jsonB64 = base64.b64encode(bytes(jsonStr, "ansi"))
goJson = GoString(jsonB64, len(jsonB64))
response = [GoString]
response = lib.RequestCertificate(goJson)
In the terminal, the DLL shows exactly what I expect.
String: eyJ1cmwiOiAiaHR0cHM6Ly9scC5ub...
But, I can't replicate this in Delphi. This is how I declared the structure that simulates a c-string:
type
TGoString = record
chars: PAnsiChar;
length: LongInt;
jsonStr := payload.ToString;
jsonBytes := TEncoding.ANSI.GetBytes(jsonStr);
jsonB64 := TNetEncoding.Base64.Encode(jsonBytes);
goJson.chars := PAnsiChar(jsonB64);
goJson.length := Length(jsonB64);
response := RequestCertificate(goJson);
But all I get is an empty reply:
String:
I already changed the declaration of my Go function to receive a c-string instead of a Go string this way:
//export RequestCertificate
func RequestCertificate(CString *C.char) *C.char{
log.Println("C String: ", CString)
goString := C.GoString(CString)
log.Println("GoString: ", goString)
The result in Python is this:
C String: 0xcbe9bef070
GoString: eyJ1cmwiOiAiaHR0cHM6Ly9scC5ub...
But in Delphi, the result is this:
C String: 0x14feb0
GoString :
I also tried to encode my Delphi string in other formats instead of ANSI, but it didn't work.
What could the reason be for this behavior? Incompatibility between Delphi and Go encoding?
I am running this in a Windows virtual machine, which runs on an Ubuntu system.