If your application (somehow) doesn't have to communicate with anything else and wait for it to respond, use `async def`, even if you don't need to use `await` inside.

---

If you just don't know, use normal `def`.

---

**Note**: You can mix `def` and `async def` in your *path operation functions* as much as you need and define each one using the best option for you. FastAPI will do the right thing with them.

		// io.Seeker, but calling Seek always returns an error and performs
		// no action. Thus, we try an innocent seek to the current position
		// to see if Seek is really supported.
		pos1, err := sr.Seek(0, io.SeekCurrent)
		if pos1 >= 0 && err == nil {
			// Seek seems supported, so perform the real Seek.
			pos2, err := sr.Seek(n-1, io.SeekCurrent)
			if pos2 < 0 || err != nil {
				return err

type ListDirResult struct {
	Entries []string `msg:"e"`
}

// ReadPartsReq - send multiple part paths to read from
type ReadPartsReq struct {
	Paths []string `msg:"p"`
}

// ReadPartsResp - is the response for ReadPartsReq
type ReadPartsResp struct {
	Infos []*ObjectPartInfo `msg:"is"`
}

// DeleteBulkReq - send multiple paths in same delete request.
type DeleteBulkReq struct {
	Paths []string `msg:"p"`

# Windows has a relatively short command line limit, which TF has begun to hit.
# See https://docs.bazel.build/versions/main/windows.html
common:windows --features=compiler_param_file
common:windows --features=archive_param_file

# Speed Windows compile times. Available in VS 16.4 (we are on 16.11). See
# https://groups.google.com/a/tensorflow.org/d/topic/build/SsW98Eo7l3o/discussion

/// tip

This is a somewhat advanced technique, and in most of the cases you won't really need it, as you can raise exceptions (including `HTTPException`) from inside of the rest of your application code, for example, in the *path operation function*.

But it's there for you if you need it. 🤓

///

{* ../../docs_src/dependencies/tutorial008b_an_py39.py hl[18:22,31] *}

  * If you are an individual writing original source code and you're sure you own the intellectual property, then you'll need to sign an [individual CLA](https://code.google.com/legal/individual-cla-v1.0.html).
  * If you work for a company that wants to allow you to contribute your work, then you'll need to sign a [corporate CLA](https://code.google.com/legal/corporate-cla-v1.0.html).

        int newNext = getNext(entry, mask);
        if (lastEntryIndex == -1) {
          // we need to update the root link from table[]
          tableSet(table, tableIndex, newNext);
        } else {
          // we need to update the link from the chain
          entries[lastEntryIndex] = maskCombine(entries[lastEntryIndex], newNext, mask);
        }

```

...without adding the required parameter `needy`, you will see an error like:

```JSON
{
  "detail": [
    {
      "type": "missing",
      "loc": [
        "query",
        "needy"
      ],
      "msg": "Field required",
      "input": null
    }
  ]
}
```

As `needy` is a required parameter, you would need to set it in the URL:

```

        // The root artifact may, or may not be resolved so we need to check before we attempt to resolve.
        // This is often an artifact like a POM that is taken from disk and we already have hold of the
        // file reference. But this may be a Maven Plugin that we need to resolve from a remote repository
        // as well as its dependencies.

        // TODO: Staging directory should be a part of the Javadocs extension
        // TODO: Pull out more of this configuration into the extension if it makes sense
        // TODO: in a typical project, this may need to be the regular javadoc task vs javadocAll

        var groovyPackageListBucket = project.getConfigurations().dependencyScope("groovyPackageListBucket");