log/field.go
func Float32(key string, val float32) Field {
	return Field{
		key:        key,
		fieldType:  float32Type,
		numericVal: int64(math.Float32bits(val)),
	}
}
func Float32(key string, val float32) Field {
	return Field{
		key:        key,
		fieldType:  float32Type,
		numericVal: int64(math.Float32bits(val)),
	}
}
// Float32 adds a float32-valued key:value pair to a Span.LogFields() record