我该如何做这样的事情（在模块变量中写入部分位置）：
nginx.conf： ...
System.InvalidOperationException: A relational store has been configured without specifying either the DbConnection or connection string to use.
at Pomelo.EntityFrameworkCore.MySql.Internal.MySqlOptions.GetConnectionSettings(MySqlOptionsExtension relationalOptions)
at Pomelo.EntityFrameworkCore.MySql.Internal.MySqlOptions.Initialize(IDbContextOptions options)
at Microsoft.EntityFrameworkCore.Internal.SingletonOptionsInitializer.EnsureInitialized(IServiceProvider serviceProvider, IDbContextOptions options)
at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>g__BuildServiceProvider|3()
at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>b__2(Int64 k)
at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.GetOrAdd(IDbContextOptions options, Boolean providerRequired)
at Microsoft.EntityFrameworkCore.DbContext.get_InternalServiceProvider()
at Microsoft.EntityFrameworkCore.DbContext.Microsoft.EntityFrameworkCore.Infrastructure.IInfrastructure<System.IServiceProvider>.get_Instance()
at Microsoft.EntityFrameworkCore.Infrastructure.Internal.InfrastructureExtensions.GetService[TService](IInfrastructure`1 accessor)
at Microsoft.EntityFrameworkCore.Infrastructure.AccessorExtensions.GetService[TService](IInfrastructure`1 accessor)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
A relational store has been configured without specifying either the DbConnection or connection string to use.
...
当我想在日志中输出自写nginx模块中的变量时，我得到
module_string = $1
但期望 uri /img/one/two/
module_string = 一/二