[Question]Why kratos load yaml as json and unmarshal to struct

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Hello @FocusHuang! 👋

I'm Dosu, a friendly bot here to assist you while we wait for a human maintainer. I'm equipped to help with bug solving, answering questions, and guiding you on your path to becoming a contributor. Don't hesitate to ask anything, I'm here to help!

The issue you're encountering seems to be related to how Go's encoding/json package unmarshals data into a time.Duration field. When a time.Duration field is unmarshaled, the encoding/json package expects the duration to be a JSON number representing the duration in nanoseconds. This is why you're seeing an error when trying to unmarshal a string like "1s" or "1h" into a time.Duration field.

However, when you're using YAML, durations can be represented as strings like "1s" or "1h", which is more human-readable than a large number of nanoseconds. This discrepancy between the JSON and YAML representations of durations is likely what's causing the issue.

One possible solution to this issue is to use a custom type for durations in your Go structs, and implement the json.Unmarshaler and json.Marshaler interfaces for this type. This would allow you to control how durations are marshaled and unmarshaled, and you could choose to use the human-readable string representation for both JSON and YAML.

Here's an example of how you could implement this:

type Duration struct {
    time.Duration
}

func (d Duration) MarshalJSON() ([]byte, error) {
    return json.Marshal(d.String())
}

func (d *Duration) UnmarshalJSON(b []byte) error {
    var s string
    if err := json.Unmarshal(b, &s); err != nil {
        return err
    }
    duration, err := time.ParseDuration(s)
    if err != nil {
        return err
    }
    d.Duration = duration
    return nil
}

With this custom Duration type, you can now use durations in your Go structs like this:

type MyStruct struct {
    Timeout Duration `json:"timeout"`
}

And you can use human-readable durations in your YAML files:

timeout: 1s

When this YAML file is loaded and unmarshaled into MyStruct, the Timeout field will correctly be a time.Duration of 1 second.

I hope this helps! If you have any further questions, please let me know.

Sources

config/config.go

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go-kratos / kratos

[Question]Why kratos load yaml as json and unmarshal to struct #3153

Sources