fix: wrap ErrProgramKilled error

This gives the caller more context on _why_ the program was killed by
wrapping the error with the context error.

tea.go

@@ -582,7 +582,7 @@ func (p *Program) Run() (Model, error) {
  model, err := p.eventLoop(model, cmds)
  killed := p.ctx.Err() != nil
  if killed {
- err = ErrProgramKilled
+ err = fmt.Errorf("%w: %s", ErrProgramKilled, p.ctx.Err())
  } else {
  // Ensure we rendered the final state of the model.
  p.renderer.write(model.View())

tea_test.go

@@ -3,6 +3,7 @@ package tea
 import (
  "bytes"
  "context"
+ "errors"
  "sync/atomic"
  "testing"
  "time"
@@ -46,7 +47,10 @@ func TestTeaModel(t *testing.T) {
  var in bytes.Buffer
  in.Write([]byte("q"))
 
- p := NewProgram(&testModel{}, WithInput(&in), WithOutput(&buf))
+ ctx, cancel := context.WithTimeout(context.TODO(), 3*time.Second)
+ defer cancel()
+
+ p := NewProgram(&testModel{}, WithInput(&in), WithOutput(&buf), WithContext(ctx))
  if _, err := p.Run(); err != nil {
  t.Fatal(err)
  }
@@ -134,7 +138,7 @@ func TestTeaKill(t *testing.T) {
  }
  }()
 
- if _, err := p.Run(); err != ErrProgramKilled {
+ if _, err := p.Run(); !errors.Is(err, ErrProgramKilled) {
  t.Fatalf("Expected %v, got %v", ErrProgramKilled, err)
  }
 }
@@ -156,7 +160,7 @@ func TestTeaContext(t *testing.T) {
  }
  }()
 
- if _, err := p.Run(); err != ErrProgramKilled {
+ if _, err := p.Run(); !errors.Is(err, ErrProgramKilled) {
  t.Fatalf("Expected %v, got %v", ErrProgramKilled, err)
  }
 }