注意：拉取文件块时，两个成功块之间的时间应该在设定时间（60秒）内完成。
Task<FileSectionResult> PullFileSectionAsync(
FileSection fileSection,
CancellationToken cancellationToken
)Function PullFileSectionAsync (
fileSection As FileSection,
cancellationToken As CancellationToken
) As Task(Of FileSectionResult)abstract PullFileSectionAsync :
fileSection : FileSection *
cancellationToken : CancellationToken -> Task<FileSectionResult> [缺少 "M:TouchSocket.Dmtp.FileTransfer.IDmtpFileTransferActor.PullFileSectionAsync(TouchSocket.Dmtp.FileTransfer.FileSection,System.Threading.CancellationToken)" 的 <returns> 文档]