go data_error ai_generated true

json: cannot unmarshal number into Go struct field User.age of type string

ID: go/json-cannot-unmarshal-number-into-string

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-05-02First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.18 active — — —
1.22 active — — —

Root Cause

The JSON payload contains a numeric value where the Go struct expects a string. The API changed, or the schema was misdeclared.

generic

中文

JSON 负载在 Go 结构体期望 string 的位置包含了数字。可能是 API 变更或结构体字段声明错误。

Workarounds

  1. 88% success 
    type User struct {
  Age json.Number `json:"age"`
}
dec := json.NewDecoder(r)
dec.UseNumber()
dec.Decode(&u)
  2. 85% success 
    Define a custom type with UnmarshalJSON that accepts both string and number.

Dead Ends

Common approaches that don't work:

  1. 60% fail

    Loses type safety and just moves the panic downstream when the value is used.

  2. 75% fail

    Leaves partially populated struct and hides real data corruption.