const auto att = dataSet.openAttribute(attributeName);
if (att.getDataType() == H5::PredType::NATIVE_DOUBLE) {
    att.read(att.getDataType(), &attributeValue);
}
else if (att.getDataType() == H5::PredType::NATIVE_FLOAT) {
    float temp = 0.F;
    att.read(att.getDataType(), &temp);
    attributeValue = static_cast<double>(temp);
}
else {
    // we throw an exception indicating we don't support the type
}

func (s *Attribute) Read(data interface{}, dtype *Datatype) error

func (s *Attribute) GetType() Identifier

if attr.GetType().ID() == hdf5.T_NATIVE_DOUBLE.ID() {
    // handle as a double
}