go encoding_error ai_generated true

json: unsupported type: map[int]string

ID: go/json-marshal-error-unsupported-type

Also available as: JSON · Markdown · 中文
90%Fix Rate
87%Confidence
1Evidence
2024-01-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
go1.19 active — — —
go1.20 active — — —
go1.21 active — — —
go1.22 active — — —

Root Cause

Attempting to marshal a Go type with keys that are not strings, which JSON format does not support (JSON object keys must be strings).

generic

中文

尝试编组键不是字符串的 Go 类型，JSON 格式不支持（JSON 对象键必须是字符串）。

Official Documentation

https://pkg.go.dev/encoding/json#Marshal

Workarounds

  1. 95% success Convert map keys to strings before marshaling: `newMap := make(map[string]string); for k, v := range oldMap { newMap[fmt.Sprintf("%d", k)] = v }` 
    Convert map keys to strings before marshaling: `newMap := make(map[string]string); for k, v := range oldMap { newMap[fmt.Sprintf("%d", k)] = v }`
  2. 90% success Define a custom struct or use a slice of key-value pairs instead: `type Entry struct { Key int; Value string }` then marshal `[]Entry`. 
    Define a custom struct or use a slice of key-value pairs instead: `type Entry struct { Key int; Value string }` then marshal `[]Entry`.

中文步骤

  1. Convert map keys to strings before marshaling: `newMap := make(map[string]string); for k, v := range oldMap { newMap[fmt.Sprintf("%d", k)] = v }`
  2. Define a custom struct or use a slice of key-value pairs instead: `type Entry struct { Key int; Value string }` then marshal `[]Entry`.

Dead Ends

Common approaches that don't work:

  1. 90% fail

    MarshalIndent also calls json.Marshal internally; same error occurs.

  2. 60% fail

    Returning nil causes json.Marshal to serialize the value as 'null', not skip it; error still may occur depending on implementation.