AWS Cognito IntitiateAuth: Missing required parameter UserName

When initializing an authentication to AWS Cognito, the API is rejecting my request:

InvalidParameterException: Missing required parameter UserName
status code: 400,

Here is the content of the request (yes, I tried putting it everywhere, no success).

params := &cognitoidentityprovider.InitiateAuthInput{
    AuthFlow: aws.String("USER_SRP_AUTH"),              // Required
    ClientId: aws.String("1i72nb4kksllrkm9s37rtyl713"), // Required
    AuthParameters: map[string]*string{
        "useame":     aws.String("myUser"), // Required
        "UserName":     aws.String("myUser"), // Required
    },
    ClientMetadata: map[string]*string{
        "useame":     aws.String("myUser"), // Required
        "UserName":     aws.String("myUser"), // Required
    },
}

Any idea about what would be the problem please? Considering to the doc (https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-dg-pdf.pdf), useame should be in AuthParameters along with srpA. Would it be possible that the problem comes from srpA? If so, what is this? It looks like that it is the password.