ClientSecrets Request return 400 status

[metaRobin]

request audio param：
audioConfig := realtime.RealtimeAudioConfigParam{
Input: realtime.RealtimeAudioConfigInputParam{
Format: "pcm16",
NoiseReduction: realtime.RealtimeAudioConfigInputNoiseReductionParam{
Type: "near_field",
},
},
Output: realtime.RealtimeAudioConfigOutputParam{
Format: "pcm16",
Voice: "alloy",
Speed: openai.Float(1.0),
},
}

http body log：
{"expires_after":{"seconds":10,"anchor":"created_at"},"session":{"model":"gpt-4o-mini-realtime-preview-2024-12-17","instructions":"You are a helpful assistant. ","audio":{"input":{"format":"pcm16","noise_reduction":{"type":"near_field"}},"output":{"speed":1,"format":"pcm16","voice":"alloy"}},"output_modalities":["text","audio"],"type":"realtime"}}

response log:
POST "https://api.openai.com/v1/realtime/client_secrets": 400 Bad Request {
"message": "Invalid type for 'session.audio.input.format': expected an object, but got a string instead.",
"type": "invalid_request_error",
"param": "session.audio.input.format",
"code": "invalid_type"
}