U.S. CSL API in Go: screen trading partners

{
  "subject": {
    "name": "Example Harbor Trading",
    "entityType": "organization"
  },
  "package": "sandbox@1",
  "retention": "standard"
}

// Go 1.22+. Standard library only. Backend or trusted CLI.
package main

import (
    "bytes"
    "encoding/json"
    "errors"
    "fmt"
    "io"
    "net/http"
    "os"
    "time"
)

func run() error {
    key, operation := os.Getenv("SANCTIONSKIT_API_KEY"), os.Getenv("SCREENING_OPERATION_ID")
    if key == "" || operation == "" { return errors.New("set the API key and a persistent operation ID") }
    path := "request.json"
    if len(os.Args) > 1 { path = os.Args[1] }
    raw, err := os.ReadFile(path)
    if err != nil { return errors.New("cannot read request file") }
    if len(raw) > 64*1024 { return errors.New("request file exceeds 64 KiB") }
    var body map[string]json.RawMessage
    if json.Unmarshal(raw, &body) != nil { return errors.New("request is not a JSON object") }
    _, sources := body["sources"]; _, pack := body["package"]
    if len(body["subject"]) == 0 || sources == pack { return errors.New("supply a subject and exactly one of sources or package") }
    request, err := http.NewRequest(http.MethodPost, "https://www.sanctionskit.com/api/v1/screenings", bytes.NewReader(raw))
    if err != nil { return err }
    request.Header.Set("Authorization", "Bearer "+key)
    request.Header.Set("Content-Type", "application/json")
    request.Header.Set("Idempotency-Key", operation)
    client := &http.Client{
        Timeout: 25 * time.Second,
        CheckRedirect: func(req *http.Request, via []*http.Request) error { return http.ErrUseLastResponse },
    }
    response, err := client.Do(request)
    if err != nil { return errors.New("transport incomplete; check the operation before retrying") }
    defer response.Body.Close()
    const limit = 8 * 1024 * 1024
    payload, err := io.ReadAll(io.LimitReader(response.Body, limit+1))
    if err != nil || len(payload) > limit { return errors.New("incomplete or oversized response") }
    if response.StatusCode < 200 || response.StatusCode >= 300 { return fmt.Errorf("screening incomplete: HTTP %d", response.StatusCode) }
    var envelope struct {
        Data *struct {
            ID string `json:"id"`
            Status string `json:"status"`
            Matches []json.RawMessage `json:"matches"`
        } `json:"data"`
    }
    if json.Unmarshal(payload, &envelope) != nil || envelope.Data == nil { return errors.New("invalid response envelope") }
    data := envelope.Data
    if data.ID == "" || (data.Status != "potential_match" && data.Status != "no_match") || data.Matches == nil {
        return errors.New("incomplete response: unexpected screening shape")
    }
    count := len(data.Matches)
    if (data.Status == "no_match" && count != 0) || (data.Status == "potential_match" && count == 0) {
        return errors.New("incomplete response: inconsistent screening shape")
    }
    return json.NewEncoder(os.Stdout).Encode(map[string]any{"id":data.ID,"status":data.Status,"candidateCount":count})
}
func main() {
    if err := run(); err != nil { fmt.Fprintln(os.Stderr, err.Error()); os.Exit(1) }
}

go run screen.go request.json

curl --fail-with-body --max-time 25 --header "Authorization: Bearer $SANCTIONSKIT_API_KEY" "https://www.sanctionskit.com/api/v1/sources"

{
  "subject": {
    "name": "Example Harbor Trading",
    "entityType": "organization"
  },
  "sources": [
    "us-csl"
  ],
  "retention": "standard"
}