1）按例子写，会报错如下：
const {error, result}= await hMysql.table('mytable').where().select().execSql();
^^^^^
SyntaxError: await is only valid in async function
2）去掉 await，返回值是一个 promise；不报错，但没有响应结果
2020-08-03 13:50:00 | SELECT * FROM mytable
undefined
3）如果只是第一句const result= hMysql.table('mytable');console.log(result);
不报错，能返回一个大对象，如下

hMysql {
connection: Pool {
_events: [Object: null prototype] {},
_eventsCount: 0,
_maxListeners: undefined,
config: PoolConfig {
acquireTimeout: 1000,
connectionConfig: [ConnectionConfig],
waitForConnections: true,
connectionLimit: 10,
queueLimit: 0
},
_acquiringConnections: [],
_allConnections: [],
_freeConnections: [],
_connectionQueue: [],
_closed: false,
[Symbol(kCapture)]: false
},
sqlObj: { table: 'mytable' },
tempObj: {},
config: {
host: 'localhost',
port: 3306,
user: 'root',
password: '‘,
database: 'exercise',
acquireTimeout: 1000,
waitForConnections: true,
connectionLimit: 10,
queueLimit: 0,
isPool: true,
defaultSqlPre: '',
isDebug: true
},
mixed: {
table: [Function: bound table],
alias: [Function: bound alias],
field: [Function: bound field],
where: [Function: bound where],
data: [Function: bound data],
order: [Function: bound order],
limit: [Function: bound limit],
page: [Function: bound page],
join: [Function: bound join],
union: [Function: bound union],
distinct: [Function: bound distinct],
lock: [Function: bound lock],
comment: [Function: bound comment],
group: [Function: bound group],
having: [Function: bound having],
count: [Function: bound count],
max: [Function: bound max],
min: [Function: bound min],
avg: [Function: bound avg],
sum: [Function: bound sum],
select: [Function: bound select],
find: [Function: bound find],
update: [Function: bound update],
insert: [Function: bound insert],
delete: [Function: bound delete],
query: [Function: bound query],
connect: [Function: bound connect],
poolEvent: [Function: bound poolEvent],
execSql: [Function: bound execSql] AsyncFunction,
transaction: [Function: bound transaction] AsyncFunction
},
isMixedWith: [Function (anonymous)],
pageNum: 1,
pageSize: 50
}