dart:ffi how to describe in dart GoString and GoSlice structures generated by go

[ghost]

Here (gist) dart and go code with generated header file.
i tried with Utf8 class from sqlite example, it's seems work.
calling add 1, 2: 3
calling cosine 2pi: 1.0
callin log��U��o��U�����U@�o��UP�o��U��o��UP�o��Uf��o��U��o��U��o��U��o��U��o��U��o��U�o��U�o��U �o��U0�o��U@�o��UP�o��U�o��Up�o��U��o��U��o��U��o��U��o��U��o��U��o��U��o��U��o��U�o��U�o��U �o��U0�o��U@�o��UP�o��U�o��Up�o��U��o��U��o��U��o��U��o��U��o��U��o��U��o��U��o��U�o��U�o��U �o��U0�o��U@�o��UP�o��U�o��Up�o��U��o��U��o��U��o��U��o��U��o��U��o��U��o��U��o��U�o��U�o��U �o��U0�o��U@�o��UP�o��U`�o��Up�o��U��o��U��o��U��o��U��o��U��o��U��o��U��o��U��o��U
1

[sjindel-google]

Here's a working Gist which uses your "Log" function:

https://gist.github.com/sjindel-google/b88c964eb260e09280e588c41c6af3e5

Note that because GoString is represented as a struct in C, you have to pass it to the Go function by pointer (*string in Go) because we don't supporting passing structs directly to native functions.

[sjindel-google]

/cc @mraleph @dcharkes

[crossle]

@sjindel-google how to return a GoString when dart call golang return string, like go code

func hello() (string, error) {
   return "", nil
}

[dcharkes]

We need support for passing structs by values in the calling convention for that. See #36730.

[sjindel-google]

In the meantime you can use a string* in Go (GoString* in C).

[crossle]

Thanks @dcharkes @sjindel-google, hope support soon.
How about the return multiple values like go return error and another value?