Why Doesn't Go's `json.Marshal` Work with Structs Containing Lowercase Field Names?

Why Does Go Fail to Generate JSON for Structs with Lowercase Field Names?

To begin, Go utilizes casing conventions to differentiate between private and public identifiers within a package. In the provided example, the fields (m_ip, m_type, and m_serial) of the Machine struct are private. Therefore, they're not accessible to external libraries like json.Marshal outside the package wherein they're defined.

Upon changing the field names to uppercase (MachIp, MachType, and MachSerial) in the second code snippet, they become public and can be exported. This allows json.Marshal to successfully generate a JSON representation.

However, if you prefer to employ lowercase field names, you can manually specify the desired JSON field names by utilizing field tags. For instance:

type Machine struct {
    MachIp     string `json:"m_ip"`
    MachType   string `json:"m_type"`
    MachSerial string `json:"m_serial"`
}

By annotating the fields with the json tag, you essentially instruct the JSON encoder to utilize the specified field names while generating the JSON output.

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